Hammock Hang Calculator
Enter the distance between your anchor trees, your hammock length, your preferred sit height, your body weight, and the hang angle you want. The calculator works out where to attach your suspension on the tree, how long your straps need to be, and how much tension each anchor must hold. Swap between metric and imperial with one click.
The physics of hammock hanging
When you lie in a hammock, your weight creates a downward force at the center. Each anchor must resist half of that force vertically, but because the suspension cord runs at an angle to the horizontal, the actual tension in the cord is much higher than just half your weight. A cord pulling at a 30-degree angle carries a tension of weight / (2 x sin 30 degrees) = weight x 1.0, meaning the cord tension equals your total weight exactly. At a flatter 10-degree angle the same formula gives weight x 2.9, so a 180 lb person creates nearly 520 lb of tension in each strap. This is why hang angle matters so much for gear safety.
Anchor height and suspension length
Once you pick your angle and know how far apart your trees are, the geometry is straightforward. The anchor point needs to be high enough that (a) the hammock bottom sits at your chosen sit height and (b) the cords descend at the target angle. The formula is: anchor height = sit height + (half anchor distance) x tan(angle). For trees 14 ft apart at 30 degrees with a sit height of 18 inches (1.5 ft), that is 1.5 + 7 x 0.577 = about 5.5 ft. The suspension strap length follows: each strap must span from the hammock end loop diagonally up to the anchor point, so strap length = (half anchor distance minus half hammock length) divided by cos(angle).
Shear force and tree health
Shear force is the horizontal component that tries to pull the two anchors toward each other. It equals weight x cos(angle) / (2 x sin(angle)), which at 30 degrees comes to about 0.87 times the body weight per anchor. This force tries to uproot or snap the tree at its base, which is why hammock users always assess trees carefully. A tree should be at least 8 inches (20 cm) in diameter, living (not dead or hollow), and free of obvious defects or decay. Wide soft webbing straps (1-2 in wide) spread the load across more bark and reduce damage compared to thin cords.
Choosing the right hang angle
The 30-degree recommendation balances three factors: lie comfort, cord load and practicality. Below 30 degrees the cords must be higher on the tree to achieve the same sit height, and the tension climbs steeply. Above 30 degrees the hammock hangs more like a seat and the tension drops, but the "lay angle" (your body diagonal relative to the hammock centerline) decreases, making it harder to lie truly flat across. Most single-layer camping hammocks need a lay angle of about 15-30 degrees off-center to produce a flat bed, which requires the suspension angle to be in the 25-35-degree range.
Hang angle comparison
| Angle | Cord tension (lb) | Shear force (lb) | Feel | Recommendation |
|---|---|---|---|---|
| 5 deg | 1033 | 1029 | Very flat lay | Avoid - extreme load |
| 10 deg | 519 | 511 | Flat lay | Use only rated gear |
| 15 deg | 348 | 336 | Slightly flat | High-rated straps only |
| 20 deg | 263 | 247 | Comfortable flat | Acceptable with care |
| 30 deg | 180 | 156 | Classic sag | Recommended standard |
| 40 deg | 140 | 107 | Deep sag | Lower tension, steeper |
| 45 deg | 127 | 90 | Deepest sag | Lowest tension option |
How cord tension and shear force scale with angle, for a 180 lb (82 kg) occupant. At 30 degrees the tension is 180 lb - equal to the load. At 5 degrees it is over 1000 lb.
Frequently asked questions
What is the ideal hang angle for a hammock?
Most hammock makers and experienced campers recommend 30 degrees as the ideal angle between the suspension cord and horizontal. At this angle the cord tension equals your body weight (one unit of tension per unit of load), the sag is comfortable, and the lay angle lets most people sleep nearly flat. Going flatter raises tension sharply; going steeper reduces tension but makes it harder to lie flat.
How high should hammock anchor points be?
The anchor height depends on your target sit height, the distance between trees, and your hang angle. Use the formula: anchor height = sit height + (half the anchor distance) x tan(angle). For a typical 14 ft spread at 30 degrees with an 18 inch sit height, the anchor sits about 5.5 ft (1.7 m) above the ground. This calculator works it out for any combination.
Why does a flatter angle create more tension?
Because the vertical component of the cord tension must equal half your weight regardless of angle, but a nearly horizontal cord has very little vertical component per unit of tension. To supply the needed vertical force, the cord must be under much greater total tension. At 5 degrees the tension is about 5.7 times your body weight per side; at 30 degrees it is exactly 1 times your body weight per side.
How long should my hammock straps be?
The suspension length depends on anchor distance, hammock body length and hang angle. The approximation used here is: suspension per side = (half anchor distance minus half hammock length) divided by cos(angle). For a 14 ft tree spacing, an 11 ft hammock and 30 degrees, each strap needs about 21 inches. Extra strap length lets you adjust once on site, so buy straps longer than the calculator suggests and use the adjustment loops.
What is shear force and why does it matter?
Shear force is the horizontal pull that tries to drag both anchors toward the center of the hammock. It equals cord tension x cos(angle). At 30 degrees it is about 156 lb for a 180 lb person. This force is transmitted through the strap to the tree bark and roots, which is why tree diameter, root depth and bark health all matter. Use wide (1-2 inch) tree straps rather than thin cord to spread the load and reduce bark damage.
How far apart should the trees be?
Most hammocks work best with anchor trees 12-17 ft (3.7-5.2 m) apart. The optimal distance is roughly 3-4 ft (1 m) more than the hammock body length. Trees closer together reduce suspension length but can push the hang angle too steep; trees farther apart may require very high anchor points to achieve the right angle and sit height.