Hammock Hang Calculator

  • Available in the Apple App Store
  • Google-Play-Badge

The Hammock Hang Calculator lets you estimate how high to install anchor points for hanging your hammock indoors (or outdoors) and also estimates the horizontal and gravitational forces applied to your hammock system. The mobile app has more customization options and includes a clinometer, so you can measure the angle of your suspension on the fly.

164 Responses

  1. scott middlebro says:

    love this calculator. hopeing that you will make an android ver. been having trouble figureing out my ridgelne length but this gave me a good place to start tyvm

  2. Love it! Even bought your book! Would love an Android app.

    • Derek says:

      Great news! The Android version is now available for both Google Play store and the Amazon app store.

      • pcdtreeman says:

        Hi
        trying out my hennessy asym again only now I have purchased your app! Question..are the angles measured before my weight 180lbs goes into the hammock(easier) or do I have to lean out of the hammock after my weight goes in (hard with integral net?) Yours overlooking something quite obvious Paul
        PS looking for the best anti mossie system in tropics ie what can I use to stop mossies coming up from underneath in warm environments?

        • Maynard says:

          My daughter and I just traveled Japan for 7 weeks using this system… from Sierra Madre Research. http://www.smrgearme.com/buy-gear/ and it solves this problem of mosquito’s in spades! We hung both of our hammocks in this Nube’ (tarp system they have created) and loved everything about it!

      • Joshua.. says:

        The link to the app in the Amazon app store is broken. A search in the Amazon app store did not find the app. Is the app not available in the Amazon store any more?

        • Derek says:

          Thanks for the update. I checked with the developer and apparently the app needs to be compatible with the Kindle in order to be listed on the Amazon App Store. The app was pulled because it isn’t compatible with Kindle. I have updated the link. I’m sorry about the confusion. Android users can access the app via Google.

      • spencer says:

        Hey, I downloaded the android version to my Samsung galaxy note8 and it keeps encountering an error. Any suggestions?

        • Derek says:

          I’ve heard this before. Some users restart or reload and it works. If that doesn’t help, send me an email and we will work with the developer.

      • Mike says:

        Seems there have been some issue’s with the android app. I noticed you stated it was being updated. Does it now work with the latest android phone software?

        • Derek says:

          It is specific hardware that has issues. Android issues are spotty and I can’t confirm with certainty which combination is having issues. I will ask the developer. We are working on a new version. New interface and features. The design has been submitted and it is in development now.

  3. Nils says:

    Hej, there is an error in the JS code of this calculator. When I’m using the metric mode, none of the forces are displayed/updated. In the file hammock-hang-calculator.html in line 170 and line 171 the forces for tension and shear are expressed as variables, but they are implemented as function. The expression for the weight force in line 172 seems to be correct but isn’t executed because of the prior error.

    Otherwise neat and easy to understand calculator. My first hammock has been shipped yesterday and I’m excited to try it out.

  4. Artie says:

    I bought your app and I got a question on a hennessey asym hammock isn’t the ridge line and hammock the same size? When I put in 15ft distance between anchors, Ridgeline and hammock length 100, preferred sit height 18, weight in hammock 170 lbs, thehang point says 41.1 inches. That is very low! If I put nothing for hammock length or ridgeline the hang point says NaN in?? Please advise

    Artie

    • Derek says:

      No, the ridgeline is not the same as the size of the hammock. The ridgeline is going to be shorter than your hammock. My Hennessy is only 9.5 ft long when laid down flat, but you’d have to detach the ridgeline in order to pull it out flat. The ridgeline is the cord that runs inside the bug net on the top where the pocket organizer lives. The ridgeline keeps the hammock in a curved shape.

      Leave a number, even if zero (0) so the app doesn’t kick back a non-number error (NaN).

  5. James says:

    Love the calculator. Hope you make a android version. Android people hammock too.

  6. Diana says:

    Is the shear force total or per side? This is a very handy calculator. I’m trying to figure out how to effectively hang my hammock in my US style home, without risking a drop from any height. ;-)

    • Derek says:

      I think what makes this confusing is the physics. There are a few forces at work here. First is the weight, or the vertical force. If you weigh 100 units, than each side would share 50 units of vertical force. If the ropes hung down at 90-degrees (straight down), the only force would be vertical. But there is also horizontal force, based on the angle of the hang. The calculator adds the horizontal force based on the angle, so each side will add up to more than half the weight that is in the hammock.

      Half the occupant weight + horizontal force = total force on each side.

      At 30-degrees, the horizontal force is half of the weight. Again, if the weight is 100:

      50 (50% of occupant weight) + 50 (horz. force) = 100 units of force applied to _each_ side.

      When you decrease the degree of the hang, you increase the horizontal force. Each side is still sharing an equal amount of vertical force, but they will _increase_ the horizontal force, meaning each side could bear _more_ force than what is being held in the hammock. This throws some folks off because it doesn’t seem to make sense that if I weigh 100 units, each side of the hammock suspension is also bearing 100 units. If you think in terms of “force” instead of “weight” it makes more sense (at least it does to me). It’s not that you magically star weighing _twice_ as much, but the forces are increasing.

      In theory, a hammock strung perfectly horizontal (0-degree hang), the horizontal force would be infinite. This is why I encourage folks to hang their hammock at an angle. :)

      • Diana says:

        Here’s where I’m confused… if the shear force is 300 units do I need two hooks that support 150 units each or two hooks that support 300 units each. I would hate for the hooks to fail and drop me 18 inches…plus I tend to wiggle/swing in my hammock. Falling is so not on my list of things to do. Especially unexpectedly while asleep. OW!

        Was much easier in Mexico where the hooks are part of the cement wall and the hooks failing seems rather impossible!

        • Diana says:

          I do appreciate your attempt to explain the physics to me and while I can grasp them theoretically, I’m just not wrapping my head around it completely. I would have probably just bought 2 hooks rated at 250 lbs and assumed I was okay, but then throwing the physics in… Argh! I haven’t had a reason to do physics for about 20 years… lol

          • Derek says:

            Ha! I’m not good at physics either; I just spent a night in a Holiday Inn Express ;) Seriously, I’ve had some help understanding this myself and I often have to refer to my notes to make sure I have it right.

        • Derek says:

          What you are looking for in gear is “safe working load.” When hammocks are rated, for example, they take the breaking strength and then reduce that by a factor to get the safe working load. For example, a hammock with a weight limit of 400 lbs will likely have a breaking strength of 1,600 lbs. This is important because they consider the dynamic aspect of hammocks, just like climbing gear: as you move about in a hammock, you exert different amounts of force. This buffer gives a safe margin of error.

          You typically want a safe working load of 4:1 or 5:1 or some go as far as 10:1. A 10:1 ratio is more common with more critical activities such as mountain climbing or hauling freight.

          A hammock with a 4:1 safe working load factor that is rated at 250 lbs has a breaking strength of 1,000 lbs. This is sufficient for the type of activity in a hammock.

          If the force is 300 lbs, you’ll want a minimum safe working load of 4:1, so you’ll want each component of your hammock system (hooks, ropes, hammock, etc.) to be safety rated above 300 lbs. It’s important to understand the difference between safe working load and breaking strength. Some suspension items, like webbing or rope, is often rated at breaking strength, so you’ll need to calculate and reduce them down to make sure they meet or exceed 300 lbs. If the hardware or soft good you purchase is “safety rated” at 300 lbs, than you should be fine. Manufacturers are required to list the ratio they used on the gear.

          For inside my home, I purchased some 3/8 in steel eye bolts. They had a safety rating of 325 lbs and they’ve been working great!

          Does this help?

          • Diana says:

            That helps a lot. I’m dealing with an older Mayan string hammock, which I love and have no concerns over a sudden failure there. My only concern was with the bolts going into the stud. I could not imagine that I could unexpectedly break a steel hook (would expect signs of stress to show before failure) BUT when it comes to suspending myself from the wall, I’d prefer not to be stupid.

      • Steve says:

        Sorry to be a pain, but your explanation of the division of the forces on the suspension lines I don’t quite get. If you have a total of 250 pounds (occupant plus the hammock, suspension and any additional gear), that is the total gravitational force acting on all points in the system. The only thing you can change is how this force is distributed (ie vertical or horizontal) . The only way you can add more overall force is if there is a ridgeline between the two hang points and this is pulled tight BEFORE adding the occupant weight. This additional force would then need to be added to the suspension line forces, but only if the ridgeline is attached on the lines below the hang points. If you are building in a safety factor by ensuring that each point will carry the total weight then I can fully appreciate that, but that should be stated in the graphic somewhere. Otherwise it is a great calculator and very helpful. Cheers.

        • Derek says:

          Steve, you have a great question and it is one often brought up, so it isn’t a pain. I had the same questions before I understood how it works.

          This is a question of physics related to practical trigonomic forces. The first thing to understand is that there is more than gravitational forces at play here. If it were just gravity, we wouldn’t need the calculator. The answer would be as simple as dividing the gravitational force in half (e.g., the weight in the hammock).

          When you push or pull against a wall, you exert force against that wall. The wall also exerts force in the opposite direction in equal amounts. When your pull force exceeds the wall’s force (e.g., its rated strength), you can pull the wall down.

          With trigonometry in play, you have to add up the total forces in play to get the final number. Gravity pulls, creating a downward force. The hammock also exerts a horizontal force/pull against the anchor point. Depending on the angle of the suspension, this horizontal force can be minimal (e.g., if the ropes are hanging straight downward), or the horizontal force could theoretically be infinite if the suspension was perfectly horizontal. Thankfully, it is impossible to achieve a perfectly horizontal force, for lots of reasons.

          To find out the total force applied to the hammock we add up all the known forces.

          Yes, you do divide the gravitational downward force, so a 100 lbs weight becomes 50 lbs of downward force on each side.

          You also take the horizontal force and divide that in half. However, the horizontal force is variable, depending on the takeoff angle of the suspension. If it is too tight, the forces are stronger. This is why the “magic” 30-degree angle is recommended beyond making it easier to sleep on the diagonal. At 30-degrees, the horizontal force is roughly the same force as the downward force. This is why a 100 lbs occupant has 100 lbs of force on both sides of the hammock. We add the 50 lbs of downward force and the 50 lbs of horizontal force to each side. If the angle were different, the horizontal force would change, but the downward force would stay the same.

          It seems almost counterintuitive that more force is being applied than there is weight in a hammock, as if you magically gain weight. You need to think in terms of forces not weight and it helps clarify the problem.

          For example, a small pebble that weighs a few grams can exert more force than its weight if it is swung in a circle, say, in a sling. This centrifugal action applies more force than just the weight of the stone. If we could put a scale under the rock while it were spinning in a circle it would register as being “heavier” than if it were just hanging straight down.

          The calculator is just for estimating, as I cannot predict all the forces at play, just those I can easily calculate for known values. For example, just sitting in a hammock adds some dynamic forces beyond a static weight. Speed and velocity of the sitting action can add more force than just the weight. Swinging in the hammock will add more force. When you consider all the forces that are or could be at play, you’ll see that this isn’t such a simple calculation at all, although the calculator itself is only doing the most rudimentary calculation.

          Understanding these forces helps clarify to me why some hammocks rip apart when the occupant claims to weigh less than the hammock is rated for. This is also why folks recommend a safe working load limit by reducing the breaking strength by a factor of 5 or more to account for the unpredictable dynamic forces at play.

          I hope this helps. Let me know if you have further questions.

          • Jaap says:

            It is not so hard.
            The only force exerted is gravitation. The rest is a matter of equilibrium of forces and moments.

            Ropes and webbing aren’t very good in transferring bending moments. If you try to, it will curve up into a bend. Which means the only force it can transfer is tension.

            Now the hammock has suspension cords on two sides and Newton’s First Law of Motions tells us that the sum of the horizontal components of all forces (the cord tension in the two suspension cords) has to add up to zero, otherwise the hammock will start moving in the horizontal plane.

            It (Newton’s Law) also tells us that the vertical components of the forces in the suspension cords have to add up to the gravitational forces exerted upon the hammock and its inhabitant(s), otherwise the hammock and its inhabitant(s) will start moving in the vertical direction. (either upward or downward)

            And finally it tells us that the sum of moments about the center of mass of the hammock and its inhabitant(s) have to add up to zero, otherwise the hammock and its inhabitant(s) will start spinning.
            Which means the gravitational force will be divided 50/50 over the two suspension cords, when the center of mass of the hammock plus its inhabitant(s) is exactly in the middle between the two suspension points. (the tree or whatever) If the center of mass is shifted towards one of the suspension points, the *vertical component* of the suspension cord tension on the side of this suspension point increases proportionally, reaching 100% of the gravitational force when the entire mass is suspended straight below one suspension point.
            As the horizontal component in one suspension cord has to remain the same as in the other (or the hammock will start moving) this also means the angle between the suspension cords and the horizontal plane will change.

            So from the equilibrium of moments and the equilibrium of vertical forces one can calculate the vertical component of the suspension force (in the suspension cord). The cord tension can then be found by dividing the vertical component by the sine of the angle between suspension cord and the horizontal plane. Finally the horizontal component can be obtained through multiplying the cord tension with the cosine of the angle, or by means of Pythagoras’ theorem.

          • fhqwgads2005 says:

            A simplified answer (with some math if you’re interested):

            Each suspension line must produce an upward (vertical) force of half the hammock’s weight in order to hold it up. If the hammock was being hung vertically by two ropes pointing straight up, the tension in each rope would be half the weight. As you move the two ropes apart, you’d notice that you weren’t just pulling upwards anymore to hold the hammock, but that you are also pulling horizontally.

            The farther apart the two ropes get, the more horizonal force is required to produce that necessary upward force to hold up the hammock (half the weight). Thus, you’ll have to add more tension to the rope to hold the same weight as the ropes move apart and the angle decreases.

            To do some math: T = tension; Fv = vertical force; Fh = horizontal force; W = weight, α = suspension angle

            In Newtonian physics, you’d draw two perpendicular force vectors, Fv and Fh, which form the legs of a right triangle, and the tension would be the sum of those forces, the hypotenuse of the triangle, along the suspension line of the hammock.

            To find the tension, we use the Pythagorean theorem:

            T^2 = Fv^2 + Fh^2

            We know Fv, it’s half the weight of the hammock, but we still need to know Fh.

            Fv = W/2

            tan(α) = Fv/Fh

            Fh = Fv/tan(α)

            Fh = W/(2*tan(α))

            Then, substitute the formulas for Fv and Fh back into the Pythagorean theorem:

            T^2 = (W/2)^2 + (W/2tan(α))^2

            T = Sqrt((W/2)^2 + (W/2tan(α))^2)

            There you have it.

            Now plug in α = 30º . Remember, tan(30) = sqrt(3)/3.

            T = sqrt(W^2/4 + W^2/(4 * (3 / 9))) = Sqrt(W^2/4 + 9W^2/12) = Sqrt(3W^2/12 + 9W^2/12) = Sqrt (12W^2/12) = sqrt(W^2) = W !!!

            If you remember common right triangles, you’d know that for a 30º triangle, the hypotenuse is twice the length of the short leg. So in this case, where the short vertical leg is Fv = half the weight, then the hypotenuse, T, is twice that, the full weight.

          • Derek says:

            This is awesome! It’s going to take me a moment to decipher some of this (I won’t claim at being a math expert).

  7. Steve says:

    I have a question on the suspension cord tension. If there are two hang points, how can each one be carrying the full weight? Or is that calculation the total between the two suspension lines? Same with the inward pull.

  8. arcticdingo says:

    Hi – and wow……….all I want to do is sling a hammock in a shady spot ! Problem as I see it is that without an even length of rope on either end then everything changes and the calculations totally did my head in !! Does the calculator only work if the hammock is slung exactly in the middle of the supports ? Do I need to have the longer rope strung higher in the tree to still achieve a comfortable level ? I also plan this to be a comfortable 2 person hammock for lounging ( maybe the magic 30 degrees changes ?? ) Any suggestions as to a good quality, affordable and durable hammock that fits the bill here ? Thanks for doing my head in – as a previous post said, ” falling is not on my to do list !! “. Cheers, Todd.

    • Derek says:

      Todd, not to worry! This calculator is more for estimating, as I mentioned in another reply, there are a lot of dynamic forces I cannot calculate for. This tool is best used as a way to figure out approximately how high to attach your hammock. For example, if you know how long your hammock is and how far apart the anchors are (e.g., inside a room) you can punch in the numbers and get the height where to set the hooks (or tree straps, etc).

      The force calculation may change if the hammock is not level and even, but I suspect that it’s not far off. I think more depends on how the weight is distributed in the hammock.

      As for a good two person hammock, I suspect you are looking for something to hang in the backyard? For casual lounging any hammock labeled “double” will do, but they won’t be cozy for sleeping long term unless you both like conjoined sleeping.

      A great hammock for lounging is the queen or ‘matrimonial’ Mayan hammock. Bar none the most comfortable hammock. Authentic Mayan hammocks sold from Hammock Rada for example are amazing. Too heavy for backpacking, but backyard hangs or car camping are perfect.

      For camping, I recommend getting separate hammocks.

  9. Deon says:

    Hi, Thanks for a fantastic resource. Could you clarify one thing for me please?
    Is the “suspension length” number for each side, or is it a total length for both sides of the suspension?

    Thanks!

  10. It’s amazing what we can do with math. I wondered growing up how these things might be useful. Its a good tool thanks.

  11. rishi says:

    well derek, i guess my question is i’m not sure why i’m not getting the ultimate hang…but maybe it’s cause i’m being careless…
    usually what i do is:
    – 1st measure the distance between the trees and input that as the distance between anchors
    – 2nd, according to the hang point the app gives me, hang hammock from that height
    – 3rd, adjust suspension length

    i may not use exact numbers but pretty close, and it usually ends up falling too low to the ground or too tight to be able to lay down flat….,

    sometimes i feel like i may be choosing tree that are too close to each other, or there’s some other variable…i’m relatively new to this, but have hung maybe 8 times or so

  12. Jason says:

    Possibly a dumb question. Can I use this even if I don’t use a ridgeline? I am planning an inside hang and don’t want a ridgeline in the way.

  13. pablo says:

    Hi! What about a hammock with spreader bars ?

    • Derek says:

      Very good question. If you’re looking for help with rope hammocks, in afraid I cannot help you. :) I’m not a fan of these tippy contraptions and would prefer if the world was rid of them. ;) Seriously though, I’m not planning to support those hammocks but the general rules apply. I do need to update the calculator for bridge style hammocks that have spreader bars. It gets tricky, though, because if the three commercially available bridge hammocks, they have different requirements.

  14. David Gilmore says:

    Since we like to hang the foot end a little higher than the head end….do you have a suggestion for the difference?

    • Derek says:

      This is an interesting request that I’m considering when updating the app. It’s really a subjective measure based on your own preferences. From the baseline, you could drop the head end lower, or raise the foot end higher as both achieve the same result. Anything from six inches to a foot is about all that’s necessary.

  15. webin says:

    I’m trying to hang two hammocks in one room, to resemble a bunk bed, a bunk hammock, I guess, but would like to divide the force of each hammock between two studs, just to be on the safe side regarding the structure of the building. I was thinking on using a 2 x 4 long enough to reach two studs (between 16 in and 24 in) placing it horizontally. my problem comes when deciding on the kind of screw eye bolt as since i’m talking about a 2 x 4, the eye bolt would have to be 2 inches long, and those are not strong enough to hold the desired weight. Then I thought of the possibility of using two eye bolts, placing one safety hook on each eye bolt and a chain hooked from each safety hook, to finally hang an extra safety hook in the middle of chain to finally hang the hammock. I’m not that heavy, just want it to be sturdy, and again be cautious with the building structure.

    Hope I’m making sense… what does the hammock experts think? would it divide all the weight between the two studs? would it be functional?

    Thank you!

  16. Mike says:

    Hi Derek. This is a great site. I have a question about the calculator. It seems like hammock length doesn’t affect strap height on the calculator. Is that correct? It seems like as you change hammock length, either the strap height or the seat height would have to change with it. I have a WBBB that I routinely hang in my backyard. I think it has the stock ridgeline, which I think is 101″. I have recently hung my Yukon hammock, which only has a 93″ ridgeline. In order to get the same sag and sit height, it feels like I need to move my tree straps up higher. When I sketch it out on a piece of paper, it seems to make sense. If your hammock is shorter, your suspension has to go farther down to connect. This would lower seat height quite a bit. If you wanted to stay out of the dirt, you would need to raise your straps. I posted this question on Hammock Forums and the people who responded seemed to agree that you need to raise the suspension with a shorter hammock. Have you considered this in the calculator, or am I off somehow? Thanks.

    • Derek says:

      Mike, given that your anchors do not change but you are changing the hammock, you should see a change in the hang point depending on what changes on the hammock.

      In my testing, I’ve found that longer, wider hammocks benefit from a deeper sag (about 45° or so) thus giving you a more dramatic diagonal. Shorter and narrower hammocks benefit from shallower sags, or in other words, a tighter pitch (about 20° or so). Most 10×5 foot hammocks, common in camping, work with a 30° hang angle typically.

      Given the same sit height for these different hammocks, you should have different hang points because the take off angle is different for each. The suspension length will also be different. I’ll look at the calculator and see if this is working correctly.

      • Mike says:

        Thanks for your answer, Derek. It makes sense. I never thought about shorter hammocks benefiting from a slightly tighter hang. I currently can’t hang my shorter hammock much tighter, because I think I would snap my ridgeline. I think I will experiment with lengthening my ridgeline a little, which should allow me to hang my shorter hammock at a little tighter (shallower) angle. This would also allow me to lower the straps a little. As always, you have given me something to think about. Thanks again.

  17. Adam Bullock says:

    I’d be really cool if this were slightly more adjustable… specifically, if the “hang point” height could be fixed to allow for an adjustment in the “distance between anchors”. For example, when hanging from underneath a porch or covered area, where none of the vertical supports are in a good place to attach the suspension, but there are horizontal support beams than run all along the edges and give almost infinite adjustability to the “distance between anchors”.

    • Derek says:

      It sounds like what you are asking is already in the app, you just have to manipulate it differently. Currently, the hang point is not editable because it is a result of the hang angle you want, the sit height, and the distance between anchors. In your example, if you need a shorter hang height but still have a wide hang distance, you will need to use a smaller hang angle.

  18. Ceri Chisholm says:

    It is not clear to me, at least in the calculations for the height of hanging a hammock, if your measurements are from: the solid part of the hammock; the bar from which al the strings attach to the hammock,; or from the ring-shaped terminal points, or from some other point on the hammock.

    • Derek says:

      You need to measure the overall length of the hammock, including the clew and steel ring. If your hammock has spreader bars, that complicates things slightly since the spreader bars raise the hammock up. You’ll have to experiment, but in my experience you will need to lower the hang point about 12 inches for spreader bar hammocks than what the calculator lists.

  19. Ryan says:

    Can’t seem to get a hang height no matter what values I put in. No fields have been left blank. Even the “reset” values give me a NaN ft value. Any help?

  20. Paul Chance says:

    This is a great aid and it would be even better if we could fix the vertical height so the parameter we can change is the suspension distance from a fixed height to hammock ends. When hanging at home, sometimes the height of supports is fixed. And sometimes, if you are not 6.5 ft tall, your reach is limited beyond 6ft. . Also, although it is easy enough to bring out the calculator to get 83% of physical hammock length for a ridge line length, it would be nice to be able to specify physical length with a check box to use 83% – or just list on the page, 83% of 8ft, 9ft, 10ft, 11ft, 12ft for reference.

  21. Graham Hicks says:

    Derek, loved your book–was reading it while I was enjoying my first hammock camping experience! Maybe enjoyed is too strong a word, since we hit record low temps (26F) for that weekend. Regardless, I’m still hanging when I get a chance. Looking at your calculator, it looks like whatever cord is used for the Ridgeline will have to be strong enough to withstand 2x the Shear Force. Am I reading that correctly? I’ve had the app installed on my iPhone for a while, but only recently took a look at it again. Since you can enter both a ridgeline and a hammock length, does the app account for the hammock sag when calculating Hang Point? In other words, will it take the sitting height, add the distance between the hammock and ridgeline, then add the vertical distance due to the suspension (based on calculations of tree distance, ridgeline length, hang angle)? Thanks!

    • Derek says:

      It should. Another user posted a similar question so l am going to look into it.

      • Graham Hicks says:

        Thanks. I’m using Lash-it for the ridgeline, and that’s listed with a 500lb strength. I just want to make sure I don’t exceed that. To keep my bug netting from dragging in the dirt, I can either stretch up higher on the trees or shallow the suspension angle (which puts more stress on the ridgeline).

        • Derek says:

          I use Lash-it myself, and even smaller line. I don’t believe it had the same tensile forces, but I’ll check in to it.

  22. Jessica says:

    I am a hammock rookie and ran across your calculator. I recently found an arbor/pergola that I want to buy to finally get our hammock hanging in our back yard. The total length of the hammock when lying flat on the ground is 145 inches. The distance between the pergola posts is 8 feet, but can be adjusted to 9 feet wide. Is this too short of a distance to hang the hammock between? When I entered these values into the calculator, it gave me a negative suspension length (-17.1 inches for the 8 foot distance and -10.1 for the 9 foot disance). Does the suspension length need to be zero or greater in my case to maintain the “magic” 30 degree hang? Hanging a hammock is apparently not as simple as I thought. :)

    • Derek says:

      Hanging a hammock is easy and straightforward, but getting a better hang, suitable for sleeping, can require more tweaking. Don’t give up!

      As to the pergola, I saw a similar one at Sam’s Club the other day. I really want one in my yard, but the prefab one at the store was about the same size you describe. It will be too small for most hammocks. Smaller hammocks that are about 9 ft long will probably work but the attachment point will be right at the limit. It won’t give you much flexibility to modify your hang. The other thing I want is the ability to use my tarp, so a pergola that has an inner distance of 12 ft is ideal. Also, after looking at the cost, I figured I could build one cheaper than buying a kit.

  23. austin says:

    I seem to have Metal studs in my wall, how would I go Of doing this?

    I already bought the eye Bolts.

    Thanks!

    • Derek says:

      I’m not qualified to answer this one :) I’ve seen some metal studs used in office buildings or steel prefab homes that don’t look like they would hold the horizontal sheering force. I’d have to ask a builder.

  24. Wilson says:

    Hello, I entered all the appropriate info into the Calculator (span between poles–8.6 ft; hammock length 13 ft; sit height, etc.) and I got as the measurement for suspension length a NEGATIVE 18.4 inches! What do I do? I can’t change the width of the span between poles. Thanks.

    • Derek says:

      The online calculator only allows you to select pre-determined (common) hang angles. Since you have such a short hang distance, you’ll have to hang the hammock up higher than normal.

  25. mary foster says:

    MY HAMMOCK stand is 10′ across I don’t know what length to order hammock for a 250# limit.

    • Derek says:

      The process doesn’t exactly work that way. If you have a hammock stand that has a fixed height and length than you’ve already limited yourself on what hammock you can buy that will fit in that space. I usually recommend folks get the hammock first. One of my favorite stands is the byer vario stand because it is adjustable and gives you more hanging options. Also, that stand, and a few others, is designed specifically for mayan-style hammocks with deeper sags. Most western style hammock stands are designed for net rope spreader bar hammocks so the height hang point is lower. This lower hang point means you can’t fit some hammocks well.

      Most parachute nylon hammocks have weight limits of 300 to 450 pounds. Steel hammock stands can hold much more than that. Depending on how high the stand is, you will be able to fit a lot of simple gathered end hammocks like the ENO DoubleNest. Look for hammocks that are less than 10 feet long for that stand.

  26. Travis says:

    Just bought the app. Dumb question, but I don’t see it answered anywhere in the app or online. Is the clinometer used when hanging the hammock or when laying or sitting in the hammock?

  27. Tosak Seelanan says:

    I bought the app for using on my iPhone 5S/iOS7.1.2. The app work great and I like it. However, it often quits when I change values — e.g. weight, ridge line, distance — in preference.and recalculate. Any fix will be appreciated.

  28. Andy says:

    I’ve bought the app and have a suggestion for the user interface – can you make the number boxes active so we can tap on them and change the number?

  29. guy thomas says:

    Derek, I bought the app for my samsung, and the clino is off 10 * right high. Is there an easy fix for this

    • Derek says:

      Thanks for the update. I’ll forward this on to the developer and see what they can find. My guess is that your internal accelerometer might need to be calibrated. If you have another app that includes a calibration tool (internal settings, perhaps?), would be one way to check.

  30. Weylan says:

    Derek, thanks for a great program.

    I used to not sleep on the ground 3 times already.

    I have been camping as a ground dweller with the family. And as a family tent camping just works out. But when I go single I can go hammock.
    But I camp in CA and may have only 1 tree and the car. So thought why not use like a handy hammock or build the 1 side like the handy hammock and the tree. And use the car wheels as anchor or build just the 2×4 at 60 degrees, but trying to get how long the 2×4 needs to be?

    And I have a Hennessey hammock.

    And while the tool can help, do you happen to know what the numbers I should use for the Hennessey hammock?

    Trying to use the most reasonably short 2×4 for the car for travel, and the 30 hang angle and balance all the forces and still try to be reasonable height off the ground at the same time.

    • Derek says:

      If you use the Handy Hammock stand, you will keep them separated just about 6 inches past the ridge line of the Hennessy. If you want to buy only one strut or make your own, just borrow the dimensions of the stand. They aren’t very tall and you can make one out of a 2×4 pretty easily if you don’t care about packing it (car camping is great for this).

  31. Adam says:

    Having huge issues with the calculator, bought this at the recommendation of a fellow hanger. I use a Nexus4, rooted, KitKat 4.4, and it will not run whatsoever. I would very much love to use this but am unable to do so..

    Please see the screenshot below..https://www.dropbox.com/s/pddzed2geo0aaqb/2014-08-14%2002.35.29.png
    Feel free to get back to me draggynsmate (at) MSN dot com.

  32. Bob Shuff says:

    Hi Derek,

    I was using the calculator to spec out a hammock stand I’m planning to build (I think you posted on the Spurtle Stand in HF). In any case, I have a HH Expedition Asym Zip coming for my son. I think you said in an early reply that the Hammock Length is 9.5′ Do you know the ridge length offhand? I assume it is fixed, but without the HH here yet I don’t know. I’m trying to figure out how tall of a stand I need for the HH. Thanks for your help and the great website and app. -Slbear

  33. Richard Donaldson says:

    Hey, the three places on the web I look for hammoxk advice is: DD, youtube and the ultimate hang. Thanks so much for everything, you’re so much help. I don’t know which android app is yours but mine works great. Now I just need to gigure how long I want my fixed ridge line :D

  34. downunder hanger says:

    Now after having had my head done in, I’m gonna do as the Mayans did all that time ago, risk happily falling to earth as Icarus did and simply string up the beast and head to the sun! Thankyou however to all of you for the analytical & entertaining ramblings and Derek for a fabulous idea…the hammock calculator.

  35. Van says:

    RE: Reader asking about hanging from steel studs…highly NOT recommended.

    RE: Vario stand and hammock length…I use a 13-ft Mayan hammock and it fits fine, although when it eventually stretches a bit, I can almost bottom out when sitting up in the middle and pushing down with my hands to exit the hammock.

    Question: Does it matter what hammock you are using when estimating hang height with the calculator? I have a 14-ft Brazilian hammock and it currently bottoms out on my Vario stand at 13-ft horizontal and 4’9″ arm height. According to the web calculator, I only need to go up 6-inches in height to have an 18-inch sit space. I would think I would need more than just 6-inches.

    • Derek says:

      The calculator will work with any size hammock. Just punch in the numbers. The problem is that a hammock stand has a fixed height and length. The other problem is that the stand flexes so the width shortens, which will also lower the sit height. Stretch in the hammock also creates an issue. The calculator doesn’t account for dynamic issues such as this. The calculator will work but if there are too many fixed variables it can’t miraculously make the stand behave differently.

      • Van says:

        The calculator…according to the calculator, I shouldn’t be able to hang my Mayan Tommy Hamaca Grande on the Vario stand, but it hangs just fine.

        • Derek says:

          Thanks Van. I glossed over which stand you have, sorry. The Vario stand is unique. I also own the Vario an it has an adjustable base and arms so it can accommodate more hammock styles. Remember that the calculator is working from fixed numbers provided by the user. You can often squeeze or stretch a hammock into places the calculator say won’t work. The app’s static calculations cannot account for dynamic changes such as fabric stretch, flex in a stand, or variations from different suspension types. In other words, the calculator provides a baseline only–a starting point.

          • Van says:

            “…provides a baseline only…” that may be okay for camping, but not when you want to install something on the walls indoors. I don’t want a bunch of holes in the walls trying to find the best place to span wall studs.

          • Derek says:

            Indoors is fine. Actually, this is where I use the calculator most because walls are static and you can easily measure and things stay put.

  36. Anastasis says:

    What about when one anchor height is different from the other. Height needs to be a variable on the calculation.
    I have a pergola and the safer place to hang it is on the top of the vertical part. So how to count the appropriate height of the other hang side?

    • Derek says:

      I’m not sure if I’m understanding clearly, so let me restate. It is common for folks to hang their hammocks with the foot end higher than the head end for increased comfort in certain situations and hammocks. The calculator doesn’t account for this because it is a simple adjustment of lifting the foot end about 6 to 12 inches higher than what is indicated in the calculator.

      If you are talking about having a fixed hang point already and are using the calculator to return the other variables, than I totally agree — this is a common feature request that I have forwarded to the developer. High on my wish list is to have direct input of the variables and the ability to “lock” certain variables, such as hang point, when those variables are not adjustable. I’ll ping the developer again and see what the timeline will be for this.

  37. John says:

    I’m still on stage one….I’m using a stud finder but can’t find the wood stud, only the steel studs. Any suggestions??

    • Derek says:

      For steel you’ll just need to use different bolts or screws. Consult with a builder to determine what you have and what kind of lateral stress they can manage.

  38. Big Carl says:

    I like the calculator, but this has been bugging me… How can it calculate sit height with a ridgeline without knowing the hammock length?

  39. Bob Jordan says:

    Derek,
    I’m 65 and just bought my first real hammock, a Warbonnet Ridgerunner.
    Q1: The calculator on my iPhone 5 returns “NaN ft” for the Hang Height even when I use the “reset” values.
    What’s needed to get it to show that value?
    Q2: How do I determine my ridgeline dimension? Is the ridgeline the length from triangle point to triangle point? If so is that laying on the ground or hung, which varies?
    Thanks for sharing your hammock Passion! Bob

    • Derek says:

      Try reloading the app. Ill also ask the developer. The ridgeline is the length from the ends of the hammock along the line that connects them when the hammock is hung. Some hammocks have a rope/line that connects these two points that is fixed, usually around 83% of the total length of the hammock fabric.

  40. Martin says:

    Hey Derek,

    Thank for putting this cool tool up! I just noticed something weird is happening when you select the Metric radio button more than once – the numbers go crazy.

  41. Bobby says:

    How would i set this up if i was using a pipe stand from your site. Based on the calculation of 12feet total length and 100inch ridge line, 30 degree hangle, yes hangle, it gives me a high of 5 feet. The specs are i believe to 72 inches, which is 6 feet. Should i go with 5feet instead of 6feet high?

  42. ken says:

    I just bought and downloaded your app for my android phone and it wont open. The first thing it says it “restart required” and the second thing it says is”runtime error, location:[313,22] ui/MainView.js Message: Uncaught TypeError: Cannot read property x of undefined, Source: left :cWatermark.x,

    Whatever all that means, i dont know.

  43. chris says:

    Hi Ken, its pretty clear there are currently issues with the calculator. Derek is doin his best. You have been offered a refund. If its not satisfactory youd best join the hammock community..hammockforums.com and like the rest of us begin the wild wonderful journey into the many and varied ways of hanging. Hell! Neither the American Indians nor the Ancient Mayan Civilisation had calculators but slept suspended in peace! Please leave us in peace quit complaining and enjoy the discovery. Ultimately there are many ways to skin a cat..the calculator is but only one! Peace.
    Downunderhanger. Australia

    • Ken says:

      I wasnt complaining, just trying to figure out a solution. I have been hammock camping for years and have just discovered that there is a correct way to do it. I didnt ask you for your smart aleck input and do not appreciate it. I was trying to resolve an issue with the app so why dont you go crawl back under a rock.

      • Derek says:

        Let’s keep it friendly guys. I didn’t take any offense from Ken’s question. Honestly, the android app has issues and I’m trying to get the developer to jump in. I’ll post an update when I hear back.

  44. PJ says:

    It’s curious you used a discontinuous variable for the hang angle, with varying gaps between the selections. Why not just make it a straight entry like the other fields? Then if your angle is 35 degrees, the calculator still tells you something.

    The formula for rope tension is T = W / (2 sin A), where T is the tension, W is the weight of the person plus gear, and A is the angle. The formula for the horizontal shear is S = W / (2 tan A). Any decent calculator app is going to have trig functions, so people can make these calculations.

  45. Phil Floyd says:

    Derek Thanks I have a android phone and the app works great. I am new to hammocks so been playing with the app a lot, plus I am 70 and hope a hammock will help us get back to camping this year.

  46. optimumrv says:

    This is fantastic, I never knew figuring out the science of hanging a hammock while camping was so easy. We will be sharing this with our network for you.

  47. Aki says:

    Are there plans for a Windows Phone version?

  48. Hi…I’m planning on hanging a hammock chair without the spreader bar…so it will basically be like a short hammock. I can’t easily access the ceiling since there’s going to be a loft above it and I don’t trust the loft to carry the load (not the weight but the swing factor) so I’m planning on attaching it to studs at two points at an angle close to the corner of a wall. Can I use the same calculator?

  49. sue says:

    I have 8 feet between two trees. We had a hammock there for years and it recently broke. Trying to find one to fit. Any idea of the length of hammock i can buy?

    • Derek says:

      If the attachment point is directly on the tree, you could use a 10 ft hammock, but it doesn’t give you much latitude for suspension. I would go with maybe a 9.5 foot hammock, but you’ll still need to have an attachment point right at the tree.

  50. Henrik Therkildsen says:

    Just bought the app for my android phone (Samsung Galaxy Note 4
    the app keeps resetting all the time. can’t get into the program.

    • Derek says:

      Hmm. Try restarting the phone. If nothing works, submit for a refund and send me any warning codes so I can tell the developer.

  51. Reign says:

    Hi there, I used your calculator hang a double Brazilian (12 feet total length) hanging in a span of 11 feet, and it’s not hung quite right but is good enough for sleeping. I’m currently trying to hang a 13 foot (total length) Nicaraguan in that same span of 11 feet. I don’t use a ridgeline, so I was wondering if hammock length was just the length of the resting area, or if it’s the total hammock length.

    Thank you

  52. Reign says:

    Great! Thank you for such a prompt reply ^_^

  53. Phil Dickinson says:

    Hi,
    I was kind of expecting a number – or do you reply? Anyway thanks
    Phil

    • Derek says:

      Phil, I must have missed your previous comment/question. I searched the spam folder too with no success. I’m sorry if your previous comment was lost, but I’m happy to respond (I try to respond to every question post to this site). You can also email me directly at theultimatehang@gmail.com.

  54. Benjamin says:

    Thanks for this calculator. I am planning to build a pergola for the purpose of hanging 4 hammocks (+1 diagonally through the middle on occasion). If you were building an ideal hammock hanging pergola, suitable for an assortment of hammocks (I currently own an ENO doublenest), what would be your ideal distance between posts (on each side), and what would be the minimum distance that would still work? Thanks!

    • Derek says:

      Awesome! I’m planning to do something exactly like that. For your plans, it really depends on if you plan to hang your hammocks for lounging or camping. For lounging, you can get by with the struts at thee minimum hang distance for your hammock, around 10 to 11 ft. If you want to hang a tarp and camp, you’ll want the struts far enough apart to clear your tarp. I was planning to do mine around 12 feet.

  55. Lisa says:

    Hi! Just bought a few 13′ hammocks for the kids to lounge on in the backyard. I have 4 pine trees in a line and was curious if there will be enough room to hang the hammocks in between or if I need to use additional posts for them. The space between the first two trees is 6′, the second space is 6’4″, and the third is 15’5″ (which I believe this one will be fine to use your calculator). I would appreciate any guidance! Thanks for your time!

    • Derek says:

      The minimum hang distance between anchor points is roughly 1 foot shorter than the hammock is long. For a 10-foot hammock, you would need a distance of about 9 feet. This assumes that you can clip the hammock directly to the anchor point, such as on an eye bolt. No suspension required. For a 13-foot hammock, you would want a distance of around 12 feet. If you try to hang a 13-foot hammock between a 6-foot span, the hammock will have to be hung very high and it would have a very deep sag. That sag may not allow you to lay in the hammock.

      If I’m hanging outdoors, even in my yard, I like to have room for a tarp so I can sleep and be protected from the elements. To make that happen, you’d want a distance of at least 12 feet to accommodate the tarp. I hope this helps!

  56. Jeff says:

    Hi

    Have a byer vario hammock stand and had a question about trying to hang 2 different hammocks (of different sizes) from the same basic setup—both Brazilian. My larger Hammock is a about 156″ in length and the shorter one is about 9.5-10ft in length (both cotton). The larger one fits fine at full height of the vertical bars and about 12ft apart. I had the shorter one initially set up with the vertical bars at the lowest point and the stand closed up as tight as it goes, connected using some nylon rope. It worked but could never really get very horizontal in it. If I made the sag more, I would hit the cross bar. Anyway thought maybe I could make the shorter one work with the setup for the larger one. I put in the length of the hammock and sit height, and then made my ropes to the the suspension height. While the hang/sag looked nice, when I lay down in it, I bottom out. Any suggestions as to how to maybe make the short Hammock work in the Vario so I could swap out the 2 different Hammocks without re-sizing the vario? Or even making the short hammock work with things closed up.

    Also, one other question. My larger hammock (156in) is cotton and pretty new. I assume it will stretch over time. Since the vario bars only seem to only extend to about 56-57in, and I’m at max height now, is my only solution to maintain the proper sag if it stretches more (and I start to hit the cross bar) to widen the distance or would doing something to shorten the end ropes be a better solution.

    Thanks. Nice site by the way. New to the whole hammock thing but enjoying it so far

    • Derek says:

      With my vario stand I found it better to adjust the stand. It is a bit of work, but not too bad. The biggest challenge with stands is the height. If the stand were taller you could use it for both hammocks without changing the stand but simply changing the hang point.

      The cotton will stretch a little over time but it shouldn’t be so bad as to bottom out.

  57. CJ McDaniel says:

    Wow….took a while to get through all the comments. Thanks, Derek, for this site. I have had hammocks for my yard for years and used them on many Boy Scout camping trips….SO much better than sleeping on rocks. Now that I have retired and am at the older years, I have been considering how to put a hammock on my back patio. I have a beautiful view to the lake to the north and the breezes all come from the south. So, my only option is between two brick columns, which are 11′-6″ apart. I love the look of the Mayan Rada and am considering that with tree straps (which I am pretty confident will work on the brick columns (they are square, so will allow for easy wrapping). I was using the calculator and want to make sure I understand the physics. The hammock I am considering is one of the twin size which is 12.79′ long with a body length of 6.3′. I think with a sit height of about 20″ or so, this should work between the columns, but want an expert opinion BEFORE I order. Am I correct in my thinking?

    Again, thanks for taking time to answer guys like me who have spent most of our lives doing other stuff (I design and build golf courses), so this is a little different math for me.

    • Derek says:

      No worries! The math is a bit different for me as well (I had help making it work). If you punch in the numbers into the calculator, it should give you the hang point. For those Mayan-style hammocks, you want to measure the complete length, from clew to clew, which would be the nearly 13 foot length you mention. Your question is whether it will fit in your 11+ foot space. I believe it will, since you will want to hang with a bigger angle, maybe 40°+ or so. The hang point will be higher up the posts.

  58. CJ McDaniel says:

    Thanks….I would just hate to order and be anticipating enjoying time in it only to find I was not smart enough to figure out it would not fit in the first place. Appreciate your input. The hammock I really want is the large, but it is 13.4′ and I am just leery of it fitting in that space without the hang angle looking stupid.

  59. Aaron says:

    What would be the formula / calculation to determine the tension on a fixed ridgeline?

    I would guess that would change the dynamics of the whole calculator if a fixed ridgeline is installed on the hammock. Now we are dealing with the angles from the suspension height affecting the load that is occurring from the hammock now a fixed angle with the ridgeline.

    I’ve been trying to determine what is the lightest weight cordage that would be appropriate for the ridgeline.

    –Aaron

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