The Sail Area-Displacement ratio (SA/D) is a calculation used to express how much sail a boat carries relative to its weight. In the first equation, the denominator in pounds is divided by 64 to convert it to cubic feet (because 1 cubic foot of salt water weights 64 pounds). The denominator is taken to the 2/3 power to make the entire metric unit-less (without this, the denominator is in cubic feet, and the numerator is in square feet). It is an indicator of the performance of a boat. The higher the SA/D, the more lively the boat's sailing performance: SA/D, however, doesn't provide information about a boat behavior in a storm or upwind. A polar diagram from a velocity prediction program gives a more precise view. See also Displacement–length ratio References Ship measurements Nautical terminology Engineering ratios Naval architecture