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.

  134 comments for “Hammock Hang Calculator

  1. scott middlebro
    August 18, 2012 at 6:54 pm

    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. September 22, 2012 at 6:00 am

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

    • Derek
      October 21, 2013 at 8:39 am

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

      • December 28, 2013 at 3:59 am

        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
          August 21, 2014 at 12:11 pm

          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..
        February 6, 2014 at 5:03 pm

        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
          February 7, 2014 at 10:49 am

          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
        June 18, 2014 at 3:10 pm

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

        • Derek
          June 19, 2014 at 5:49 am

          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.

  3. Nils
    October 10, 2012 at 11:44 am

    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.

    • Derek
      October 12, 2012 at 11:16 am

      Thanks! I’ve fixed the code and it looks like it is working correctly now.

  4. Artie
    December 5, 2012 at 2:19 pm

    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


    • Derek
      December 5, 2012 at 11:14 pm

      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
    May 10, 2013 at 8:52 am

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

    • Derek
      May 10, 2013 at 10:00 am

      I know, I know :) I’m looking for a developer. It’s not for lack of desire, but lack of funding.

  6. May 23, 2013 at 6:16 pm

    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
      May 23, 2013 at 7:48 pm

      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. :)

      • May 23, 2013 at 8:34 pm

        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!

        • May 23, 2013 at 8:40 pm

          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
            May 23, 2013 at 9:31 pm

            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
          May 23, 2013 at 9:28 pm

          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?

          • May 23, 2013 at 9:45 pm

            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
        June 15, 2013 at 7:16 pm

        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
          June 15, 2013 at 10:10 pm

          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
            September 18, 2013 at 4:25 pm

            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.

  7. Steve
    June 15, 2013 at 6:59 pm

    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. June 26, 2013 at 2:47 pm

    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
      June 26, 2013 at 3:32 pm

      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
    September 5, 2013 at 9:02 am

    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?


    • Derek
      September 5, 2013 at 9:12 am

      Deon, the length is for each side.

  10. September 8, 2013 at 11:34 am

    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
    September 9, 2013 at 8:51 am

    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
    September 14, 2013 at 2:25 pm

    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.

    • Derek
      September 14, 2013 at 6:26 pm

      Yes! The ridge line is not a necessity. Use as normal and remove the ridge line length.

  13. September 28, 2013 at 8:19 pm

    Hi! What about a hammock with spreader bars ?

    • Derek
      September 28, 2013 at 8:40 pm

      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
    October 21, 2013 at 1:21 pm

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

    • Derek
      October 21, 2013 at 2:39 pm

      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.

      • David Gilmore
        October 21, 2013 at 6:07 pm

        Thanks for the reply!

  15. webin
    December 24, 2013 at 1:43 am

    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!

    • Derek
      December 24, 2013 at 2:14 pm

      In one room, I have three eye bolts drilled into one stud. The studs I picked are on key frames so there are multiple studs together. I’m not sure if that really matters, but it works.

      • webin
        December 27, 2013 at 4:10 pm

        thank you

  16. Mike
    December 29, 2013 at 5:43 pm

    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
      December 29, 2013 at 10:13 pm

      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
        January 5, 2014 at 10:18 am

        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. January 24, 2014 at 11:39 am

    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
      January 24, 2014 at 1:43 pm

      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
    March 13, 2014 at 11:01 pm

    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
      March 13, 2014 at 11:10 pm

      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
    March 25, 2014 at 3:59 am

    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?

    • Derek
      March 25, 2014 at 5:49 am

      Which calculator are you using? The online version or one of the mobile apps? Send me a PM to theultimatehang@gmail.com and we will try to debug.

  20. Paul Chance
    April 11, 2014 at 7:32 pm

    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.

    • Derek
      April 11, 2014 at 7:52 pm

      Great thoughts. Let me see what I can do.

  21. Graham Hicks
    May 20, 2014 at 7:03 am

    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
      May 20, 2014 at 8:24 am

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

      • Graham Hicks
        May 20, 2014 at 12:15 pm

        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
          May 20, 2014 at 3:07 pm

          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
    May 20, 2014 at 12:31 pm

    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
      May 20, 2014 at 3:13 pm

      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
    May 20, 2014 at 1:23 pm

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

    I already bought the eye Bolts.


    • Derek
      May 20, 2014 at 3:15 pm

      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
    June 17, 2014 at 9:05 am

    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
      June 17, 2014 at 8:13 pm

      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. June 22, 2014 at 6:54 pm

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

    • Derek
      June 22, 2014 at 10:20 pm

      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
    June 26, 2014 at 8:44 am

    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?

    • Derek
      June 26, 2014 at 10:41 am

      The most accurate measurement is if there is some tension to take up the slack, but not fully loaded.

  27. Tosak Seelanan
    July 17, 2014 at 7:57 am

    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.

    • Derek
      July 20, 2014 at 12:52 pm

      Thank you for the feedback. I’ll send this on to the developer.

  28. July 29, 2014 at 3:24 am

    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?

    • Derek
      July 29, 2014 at 7:10 am

      Great idea!

  29. guy thomas
    July 30, 2014 at 2:09 pm

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

    • Derek
      July 30, 2014 at 10:08 pm

      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
    August 8, 2014 at 8:43 pm

    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
      August 12, 2014 at 11:14 pm

      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
    August 17, 2014 at 5:18 pm

    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.

    • Derek
      August 17, 2014 at 7:28 pm

      Thanks. I’ll forward this to the developer.

      • Adam
        September 19, 2014 at 11:40 am

        Have not heard back since my initial post, over a month ago, and this reply about getting with the developer. Is there an issue running this on a Nexus 4, rooted, running KitKat 4.4 or am I going to be looking for another piece of software ?

        • Graham Hicks
          September 19, 2014 at 11:59 am

          What other software? :)

          • Adam
            September 19, 2014 at 12:59 pm

            There is another one out there but I would prefer to support the developer hence the reason for the purchase, just like the purchase of the book. Its called Hammock Tools I believe..

          • Derek
            September 19, 2014 at 8:21 pm

            Well, I’ll try to persuade the developer to get on task.

        • Derek
          September 19, 2014 at 8:20 pm

          Adam, I wish I had a better answer for you. My developer is very busy right now so changes are not yet available.

          • Adam
            January 30, 2015 at 2:11 pm

            Any further luck on this end ? Still have the rooted Nexus 4 running 4.4 and still experiencing the same errors.. Just checking to see if there has been any additional headway?

        • Graham Hicks
          September 19, 2014 at 11:49 pm

          Hammock Tools might not be available anymore–couldn’t find it on the app store.

  32. Bob Shuff
    September 9, 2014 at 10:35 am

    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

    • Derek
      September 9, 2014 at 6:25 pm

      I believe it is 100 inches on the ridge line.

  33. Richard Donaldson
    September 10, 2014 at 8:58 am

    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
    September 16, 2014 at 7:55 am

    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
    September 18, 2014 at 10:05 pm

    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
      September 19, 2014 at 12:13 am

      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
        September 19, 2014 at 9:59 pm

        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
          September 21, 2014 at 10:18 am

          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
            September 21, 2014 at 1:51 pm

            “…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
            September 21, 2014 at 6:47 pm

            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
    September 19, 2014 at 9:32 am

    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
      September 19, 2014 at 11:23 am

      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.

      • Anastasis
        September 20, 2014 at 10:40 am

        Thank you!

  37. John
    October 6, 2014 at 4:31 pm

    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
      October 13, 2014 at 10:01 pm

      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
    October 17, 2014 at 11:09 am

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

    • Derek
      October 17, 2014 at 12:19 pm

      It must use default values. I’ll look in to it.

  39. October 26, 2014 at 7:28 am

    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
      October 26, 2014 at 7:49 am

      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
    November 11, 2014 at 11:50 am

    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.

    • Derek
      November 11, 2014 at 12:30 pm


  41. Bobby
    January 25, 2015 at 7:50 am

    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?

    • Derek
      January 25, 2015 at 8:37 am


  42. Pingback: Hammock campers
  43. ken
    January 29, 2015 at 6:10 am

    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.

    • Derek
      January 29, 2015 at 6:21 am

      Ken, I’m checking with the developer.

    • ken
      January 29, 2015 at 6:26 am

      I just uninstalled it and re installed it and i keep getting the same code as above. By my calculations, i just paid twice and still cannot use it.

      • Derek
        January 29, 2015 at 6:28 am

        I’m checking with the developer. In the meantime, contact the App Store to get a refund.

        • ken
          January 29, 2015 at 7:09 am

          I deleted the app again and contacted Goggle for a refund but would still like to have the app.

          • Derek
            January 29, 2015 at 7:50 am

            Of course! I want you to enjoy the app too. The developer is looking at it. I wish I had more control over the code, but I don’t.

  44. chris
    January 29, 2015 at 7:26 am

    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
      January 30, 2015 at 12:39 pm

      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
        January 30, 2015 at 2:05 pm

        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.

        • ken
          February 9, 2015 at 3:50 pm

          Any new yet on what was going on with my download?

  45. PJ
    February 9, 2015 at 8:35 pm

    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.

  46. Phil Floyd
    February 22, 2015 at 3:55 pm

    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.

  47. March 2, 2015 at 12:03 am

    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.

  48. Aki
    March 17, 2015 at 12:29 am

    Are there plans for a Windows Phone version?

    • Derek
      March 18, 2015 at 11:49 am


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