What this calculator does
A comfortable hammock hangs with about a 30 degree strap angle and a ridgeline roughly 83% of the distance between anchors. At four metres between trees that is a 3.32 m ridgeline.
The 83% figure is the useful one, because it fixes the sag independently of how far apart the trees are. A hammock hung too tight is uncomfortable and puts far more load on the anchors; the 30 degree angle roughly halves the strap tension compared with hanging it flat, which matters for both comfort and the trees.
The formula
The suggested ridgeline is 0.83 times the anchor distance, which is the commonly used rule for a comfortable sag. The hang-point drop is half the anchor distance multiplied by the tangent of the strap angle, giving how far below the anchor points the hammock ends should sit. The ridgeline does not change with strap angle, since it is set by the hammock rather than the hang.
| Term | Meaning |
|---|---|
| Ridgeline | A line between the two hammock ends that fixes the sag, typically 83% of the hammock length. |
| Strap angle | The angle the suspension makes with horizontal. 30 degrees is the usual target. |
| Hang-point drop | How far below the anchor the hammock end sits. |
| Sit height | Where the middle of the hammock ends up, ideally about chair height off the ground. |
The inputs explained
| Field | What to enter |
|---|---|
| Distance between anchors (m) | Distance between the two anchor points in metres. |
| Strap angle from horizontal (°) | Strap angle from horizontal in degrees. 30 is the usual recommendation. |
When to use it
Setting up between two trees
The anchor distance is whatever the trees give you, and the calculation converts that into where the straps should attach.
Getting a flatter lie
Hanging with more sag and lying diagonally is what produces a flat lie, and the ridgeline is what makes that repeatable rather than guesswork.
Reducing load on the anchors
A shallower strap angle multiplies the tension considerably, so hanging at 30 degrees rather than 10 is easier on both the straps and the trees.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does strap angle change the hang?
A fixed anchor distance across a range of strap angles.
| Strap angle | Hang-point drop below anchors | Suggested ridgeline length | In feet |
|---|---|---|---|
| 20° | 0.73 m | 3.32 m | 10.89 ft |
| 25° | 0.93 m | 3.32 m | 10.89 ft |
| 30° | 1.15 m | 3.32 m | 10.89 ft |
| 35° | 1.40 m | 3.32 m | 10.89 ft |
Questions
What is the 30 degree hang angle?
The angle the suspension straps make with horizontal, and the widely used target for a comfortable hammock. It gives enough sag for a flat diagonal lie and keeps strap tension reasonable. Hanging much flatter both tightens the hammock uncomfortably and multiplies the load on the anchors.
What does a ridgeline do?
It fixes the sag at a repeatable amount regardless of how far apart the anchors are, so the hammock hangs the same way every time. Without one, the lie depends entirely on how tight you pulled the straps, which is difficult to reproduce.
Why does a tight hang increase strap tension?
Because the suspension has to resist your weight with a force that grows as the angle flattens. At 30 degrees the tension is roughly equal to your weight; at 10 degrees it is nearly three times it. A tight hang is the usual reason straps and hardware fail.
How high should I hang it?
So the lowest point sits about chair height, roughly 45 cm off the ground, which makes getting in and out easy and limits the fall. The drop figure here tells you how far below the anchors the ends sit, which combined with the sag gives the height at the middle.
For tent sizing instead, see the tent size calculator. For firewood for the same trip, see the firewood calculator.