Sailing Speed (Hull Speed) Calculator

Work out sailing speed (hull speed) instantly with clear inputs, formula shown and shareable results.

About Sailing Speed (Hull Speed) Calculator

Hull speed is 1.34 times the square root of waterline length in feet — the practical ceiling for a displacement hull. Whether a boat reaches it depends on the sail area to displacement ratio: below 15 is under-powered, 16-18 is typical for a cruiser, and above 20 is performance oriented.

Formula

Hull speed

V = 1.34 x sqrt(LWL in feet); SA/D ratio = sail area (ft2) / displacement (ft3)^(2/3)

Worked example

With the default values below, Sailing Speed (Hull Speed) Calculator returns Hull speed of 7.60. Change any input above and every figure here is recalculated in your browser.

Inputs used

Waterline length: 9.8 m
Displacement: 5.2 t
Sail area: 48 m²
True wind speed: 14 kt

Results

Hull speed: 7.60 kt
Estimated boat speed: 7.27 kt
Sail area to displacement ratio: 16.258
Speed to length ratio: 1.282

Step by step

1Values used
2Hull speed
3Hull speed= 7.60 kt
4Estimated boat speed= 7.27 kt
5Sail area to displacement ratio= 16.258
6Speed to length ratio= 1.282

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Can a sailing yacht exceed hull speed?

Only surfing down waves or planing, which needs a light hull and a lot of sail. Heavy cruisers effectively cannot.

Why does waterline length matter more than overall length?

Because the wave system is generated by the immersed hull. Overhangs contribute nothing until the boat heels and immerses them, which is why hull speed rises slightly when heeled.