How this instrument works
A ridgeline is a fixed-length strap or cord connecting a hammock's two suspension points, set to a specific length so the hammock hangs at a consistent, comfortable sag every time — a real improvement over eyeballing knot position on the suspension straps, which is hard to reproduce precisely from one hang to the next. Get the ridgeline length wrong and the hammock either hangs too flat (uncomfortable, and puts more outward tension stress on the fabric's edges) or too deep (a pronounced 'taco' shape that's equally uncomfortable in a different way).
The commonly cited practical shortcut sets ridgeline length to 83% of the hammock's total length, a rule of thumb widely repeated among hammock campers that works reasonably well across a typical range of hang angles without requiring any trigonometry. This calculator also computes the exact trigonometric relationship — ridgeline length equals hammock length times the cosine of the hang angle — which lets you dial in a specific angle rather than relying on the fixed 83% shortcut alone.
A widely recommended starting hang angle for the suspension lines is around 30 degrees from horizontal, a sweet spot commonly cited for balancing comfortable sag against manageable tension on the suspension system. This calculator covers ridgeline length only — it doesn't calculate suspension cord tension or how high to set your anchor points, both of which depend on additional factors like tree spacing and desired sag height beyond what this calculator's two inputs capture.
- Enter your hammock's total length, in feet.
- Enter your target hang angle — 30 degrees is a commonly recommended starting point.
- Read the ridgeline length from the quick 83% rule of thumb.
- Read the ridgeline length from exact trigonometry at your chosen angle.
- When cutting or tying your ridgeline, err slightly short rather than long — you can always let more cord out, but an overly long ridgeline sags flatter than intended.
Worked example — an 11-foot camping hammock
An 11-foot gathered-end camping hammock using the quick rule of thumb: 11 × 0.83 = 9.13 feet of ridgeline needed.
The exact trig figure at the commonly recommended 30-degree hang angle: 11 × cos(30°) = 11 × 0.866 = 9.53 feet — within about four inches of the rule-of-thumb figure, which is exactly why the 83% shortcut has stuck around as a fast, no-math approximation for anyone hanging at or near that standard angle.
Questions
What exactly is a hammock ridgeline, and do I actually need one?
A ridgeline is a fixed-length line connecting a hammock's two suspension points along the top, setting a consistent sag depth every time you hang it rather than relying on judging knot position by eye. It isn't strictly required — some hammock campers hang without one — but it makes achieving the same comfortable sag repeatable across different trees and setups, which is why many campers add one.
Why do the two ridgeline figures (rule of thumb vs. trig) come out slightly different?
The 83% rule of thumb is a fixed approximation that doesn't change with hang angle, while the trig calculation is exact for whatever specific angle you enter — the two align closely near the commonly recommended 30-degree angle, but diverge more noticeably if you choose a flatter or steeper hang angle than that reference point.
What hang angle should I use?
A widely cited starting point is around 30 degrees from horizontal, commonly recommended as a comfortable balance between a flat, tension-heavy hang and an overly deep, 'taco'-shaped one. Personal preference and hammock style can shift that somewhat — some campers prefer slightly flatter or deeper hangs — so treat 30 degrees as a solid default to adjust from rather than a strict rule.
Does this calculator also tell me how high to set my anchor points?
No — anchor height depends on additional factors beyond hammock length and hang angle, including tree spacing and how much sag you want at the lowest point of the hammock, none of which this calculator's two inputs capture. This calculator is scoped specifically to ridgeline length.
What happens if my ridgeline is too long or too short?
A ridgeline that's too long lets the hammock hang flatter than intended, which reduces the wrap-around comfort a proper sag provides and increases outward tension stress on the fabric's edges. One that's too short forces an overly deep, pronounced curve that can feel constricting — getting the length right (or close to it, using either figure this calculator provides) noticeably improves comfort.