Hull Speed Calculator
The theoretical top speed of a displacement hull from its waterline length — the wall a sailing boat runs into.
A displacement hull makes a wave as long as its waterline; past a speed-to-length ratio of about 1.
How the hull speed calculator works
A displacement hull makes a wave as long as its waterline; past a speed-to-length ratio of about 1.34 it would have to climb its own bow wave, which takes far more power than most sails or engines have. Hull speed in knots is 1.34 × √(waterline length in feet). Planing hulls and multihulls are not bound by it.
Formula: hull speed (knots) = 1.34 × √LWL (ft)
Worked examples
| Inputs | Hull speed | Note |
|---|---|---|
| 9 m waterline | 7.28 knots | 7.28 knots |
| 30 ft waterline | 7.34 knots | 7.34 knots |
| A 100 ft schooner | 13.4 knots | 13.40 knots |
FAQFrequently asked questions
What is a displacement hull?
One that pushes through the water rather than skimming over it — most sailing yachts, trawlers and canal boats. Planing hulls (speedboats) and multihulls escape the hull-speed limit.
Why 1.34?
It is the speed-to-length ratio at which the hull’s own bow wave is as long as its waterline, so going faster means climbing that wave. Light or narrow hulls can push to 1.4–1.5.
Can a boat go faster than hull speed?
Yes, with enough power — but resistance rises very steeply beyond it, so a small engine or an ordinary sail plan stalls just under it. Surfing down a wave is the usual exception.
What is waterline length?
The length of hull actually in the water, bow to stern, at normal load — shorter than the overall length because of the overhangs. Use LWL, not LOA.
Where these figures come from
- World Handicap System — Rules of Handicapping — the score differential and handicap index formula
- International Cricket Council — Playing Conditions — over structure and run-rate definitions
- Cricket Australia — the national body for the sport these statistics most often describe here
Last checked: September 2026. Formulas follow the governing bodies where one publishes them — the World Handicap System for golf, the ICC playing conditions for cricket run rates.