The 30° rule
Hammock campers have a simple rule: hang the suspension at about 30° from horizontal. At that angle the hammock sags enough to lie diagonally and flat, and the pull on each tree is about equal to your body weight. Hang it tight and flat like a banana and the forces multiply; hang it too steep and the hammock squeezes you like a cocoon.
What this calculator does
It treats the hammock and its straps as two straight lines from each anchor down to the lowest point, at your chosen angle. From that it finds:
- Hang point height = sitting height + half the distance between anchors × tan angle;
- Strap length per side = half the distance ÷ cos angle − half the hammock length;
- Pull on each anchor = your weight ÷ (2 × sin angle).
Real fabric sags in a curve, so treat the results as a starting point and fine-tune on site.
Example
Two trees 15 ft apart, an 11 ft hammock, a sitting height of 18 in and a 30° hang:
- hang points at about 1.5 + 7.5 × 0.577 ≈ 5.8 ft (70 in) up each tree;
- about 3.2 ft of strap on each side;
- each tree holds about your own weight, here 180 lb.
How the angle changes the forces
| Hang angle | Pull on each anchor |
|---|---|
| 10° | 2.9 × your weight |
| 20° | 1.5 × your weight |
| 30° | 1.0 × your weight |
| 45° | 0.7 × your weight |
Tips for a good hang
- Pick anchors about 12 to 18 ft apart for a typical 10 to 11 ft hammock.
- Use tree straps at least 1 in (2.5 cm) wide to protect the bark; many parks require them.
- A structural ridgeline about 83% of the hammock length keeps the same sag every time.
- Choose live, healthy trees at least 6 in thick, and look up for dead branches before you hang.
- Lie slightly diagonally to get a flatter position.
Check the weight rating of the hammock and of every strap, carabiner and buckle. Dynamic loads, such as dropping into the hammock, briefly multiply the forces.