Sailboat calculators
These are the same design-ratio computations Knotworth runs in its free pre-check of any listing. If you want them calculated automatically from a real boat ad, paste the URL on the homepage; if you want the theory, start with the design ratios guide.
Hull speed calculator
Waterline length in, theoretical hull speed out, in knots and km/h. With an honest note on what hull speed does and does not mean for a cruising boat.
Open calculator →Capsize screening calculator
Beam and displacement in, capsize screening formula value out, read against the conventional 2.0 offshore threshold and its known limitations.
Open calculator →All design ratios
One form, six numbers: sail area to displacement, displacement to length, ballast ratio, Brewer comfort ratio, capsize screening and hull speed.
Open calculator →Knotworth reads the specs straight from any listing URL and computes every ratio in the free pre-check, alongside mission fit and the costs the ad doesn't mention.