Mainsheet Load Calculator

Foot length of main in feet
Luff length of main in feet
Apparent wind speed in knots
Distance from aft end of boom to
mainsheet attachment point in feet (* see note below)

Mainsheet load in pounds

©2002 by Joseph Oster - All Rights Reserved.


  1. * "D" is actually the distance from the clew ("E") and would be a negative number if the mainsheet attaches aft of the clew.
  2. This calculator uses the following formula suggested by Harken:
    M = (E^2 x P^2 x 0.00431 x V^2) / ( sqrt(P^2 + E^2) x (E - D) )
  3. An alternate method from AYRS has been suggested using Sail Area (SA), Camber and Leech Sag. If one assumes camber to be 12.5% and leech sag to be 6.5%, the formula can be simplified into:

    Clew load = SA x V^2 / 100

    Result of that formula, assuming SA = (E * P) / 2:

Also: Ideal Boat Hull Calculator

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