Sailing calculators
The performance ratios on our yacht pages, as calculators you can play with. Enter your own numbers in metric or imperial, or load the specs of any boat in the catalogue, and see where the result sits among boats of the same type and length. Every calculator explains its formula, how to read it and where it falls short.
Hull speed calculator
Hull speed in knots from waterline length: 2.43 × √LWL in metres (1.34 × √LWL in feet), with a comparison against similar boats.
Sail area / displacement calculator
Work out a sailboat's SA/D ratio from sail area and displacement, in metric or imperial units, and see how it compares with boats of the same size.
Displacement / length calculator
Calculate the displacement/length ratio of a sailboat from displacement and waterline length, from ultralight to very heavy, with peer context.
Comfort ratio calculator
Ted Brewer's motion comfort ratio from displacement, waterline, length overall and beam, in metric or imperial, compared with similar boats.
Capsize screening calculator
The capsize screening formula from beam and displacement, against the 2.0 offshore guideline, with a comparison against boats of the same size.
Ballast / displacement calculator
Ballast as a percentage of displacement, what the number says about stiffness, and where a boat sits among its peers.
Bruce number & KSP calculator
Bruce number and Kelsall's KSP for catamarans and trimarans, from sail area, displacement and waterline length, with peer context.
Unit converter
Convert sailboat specifications between metric and imperial: metres and feet, kilograms and pounds, square metres and square feet, litres and US gallons.
The formulas are the classic ones, with the constants for seawater, and give the same values as the ratios on our yacht pages. See Sources & methodology for where the specifications come from.