The Yacht Ratio Calculator is a device to how a sailing yacht is likely to perform at sea, within the results there will naturally be some degree of flexibility. For example the maximum hull speed (for displacement boats) can vary according to the amount of heel as many yachts have a greater waterline length when sailing in a stiff breeze. The ratios that concern the square feet/metres of sail are calculated on the manufactures figures for a standard sail plan, not with 1/2 furled or storm jibs! Treat the results as a guide only. I have entered the metrics for a number of popular cruising yachts immediately below, or, you can enter the details of any yacht you like if you already know their measurements. Remember to select either the Metric/Imperial radio buttons.

If you are not sure about the exact specifications for the yacht you own, or are interested in, I have put a link to in the menu. There you will find thousands of statistics of sailing yachts old and new.

Fair winds

Metric or Imperial (feet & lbs or mtrs & kg)

Length at waterline m/ft
Length overall m/ft
Beam m/ft
Displacement kg/lb
Ballast kg/lb
Sail area m2/ft2
very good
Max hull speed 0
Ballst / Weight ratio 0%
Sail / Displacement ratio 0
Displacement / Length ratio 0
Capsize Screening ratio 0
Motion Comfort ratio 0

This ratio was invented by Ted Brewer who say's he dreamed it up "tongue in cheek" as a measure of the motion comfort of a boat. A boat that has a more corky motion is considered less comfortable then one less affected by wave action. A higher value is better (if you like comfort). Smaller and beamier boats tend to have a lower ratio. This is best used to compare boats of similar size. A 26 footer should probably not be compared to a 40 footer using this ratio. The ratio is a factor of LOA and LWL and it may assume that boats with long overhangs tend to have wineglass shaped cross sections which provide more gradual buoyancy as they are immersed. However, a boat like a Valiant 42 has a long LWL for it's LOA and possesses this more wineglass shaped cross section. The ratio also favors displacement (higher gives larger result) and there is no accounting for distribution of weight. It also takes no account of waterline beam, a value that can be quite informative but is rarely available on stat sheets.

"Ratios will vary from 5.0 for a light daysailer to the high 60s for a super heavy vessel, such as a Colin Archer ketch. Moderate and successful ocean cruisers, such as the Valiant 40 and Whitby 42, will fall into the low-middle 30s range.

Do consider, though, that a sailing yacht heeled by a good breeze will have a much steadier motion than one bobbing up and down in light airs on left over swells from yesterday's blow; also that the typical summertime coastal cruiser will rarely encounter the wind and seas that an ocean going yacht will meet. Nor will one human stomach keep down what another stomach will handle with relish, or with mustard and pickles for that matter! It is all relative." (Ted Brewer)