Displacement-length ratio

The displacement-length ratio is a nondimensional measure of how heavy a hull is for its waterline length, computed as displacement in long tons divided by (0.01 times LWL in feet) cubed, D/L = Disp_LT / (0.01 LWL)^3. Both numerator and denominator are volumes, so the ratio is dimensionless despite its mixed-unit definition. Low values, under about 100 to 150, mark light, easily driven racing and planing hulls; values above 300 to 400 mark heavy cruising and working displacement hulls. The ratio sorts hulls by displacement-driven resistance and hull-speed behavior and is a standard first-cut comparator in yacht and small-craft design, read alongside the prismatic coefficient and the sail-area-displacement ratio.