# Displacement–length ratio

The displacement–length ratio (DLR or D/L ratio) is a calculation used to express how heavy a boat is relative to its waterline length.[1]

DLR was first published in Taylor, David W. (1910). The Speed and Power of Ships: A Manual of Marine Propulsion. p. 99.[2]

It is calculated by dividing a boat's displacement in long tons (2,240 pounds) by the cube of one one-hundredth of the waterline length (in feet):[3]

${\displaystyle {\mathit {DLR}}={\frac {{\mathit {displacement}}(\mathrm {lb} )~/~2240}{(0.01\times {\mathit {LWL}}(\mathrm {ft} ))^{3}}}}$

DLR can be used to compare the relative mass of various boats no matter what their length. A DLR less than 200 is indicative of a racing boat, while a DLR greater than 300 or so is indicative of a heavy cruising boat.

Displacement DLR
ultralight under 90
light 90 to 180
moderate 180 to 270
heavy 270 to 360
ultraheavy 360 and up