Keelboat Metrics Calculator


Use the following form to calculate a sailboat standard metrics. The formulae are given at the end of this page.

The pre-loaded measurements are that of a Tanzer 7.5 - Just override them with your own values, then click the Calculate! button.

For more information on sailboat metrics, consult the Ted Brewer Yacht Design website.

The Calculator

Your Boat Measurements:

  • Select a Unit System (Please be consistent or the results will be meaningless):


Your Boat Standard Metrics:

Metrics formulae explained:

All figures are based on the British Measurement Mystem.

Note: some Displacements are in British Tons (2,000 lbs), some in Long Tons (2,240 lbs).

Metrics Formula
Sail Area - Displacement Ratio Sail Area / (Displacement in Cubic Feet)2/3
Displacement - Length Ratio (Long Ton Displacement) / (0.01 * LWL)3
Theoretical Hull Speed 1.34 * (LWL)1/2
Motion Comfort Displacement / { 2/3 * [ (0.7 * LWL) + (1/3 * LOA) ] * Beam4/3 }
Ballast - Displacement Ratio (Ballast / Displacement) * 100
Capsize Screening Formula Beam / (Displacement in Cubic Feet)1/3
In the above formulae:
Displacement in Cubic Feet = Displacement in lbs / 64
Displacement in Long Tons = Displacement in lbs / 2,240

Calculator designed by D. Servranckx. Page updated on 2022-11-26.

********** NOTE: This page must be edited as "the Boss". ********** Update log: 2022-11-26_ DS: fixed "balast" to "ballast" spelling. 2022-08-16: DS: minor display tweaks. 2022-01-12: DS: updated default Tanzer 7.5 data using Wikipedia data. 2022-01-11: DS: changed the Motion Confort formula TEXT to show (4/3) instead of (3/4) 2021-04-30: DS: added this section. replaced "Keel Boat" with "Keelboat"

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