OYRA Displacement to Length Ratio Formula

To differentiate between long, spread-out hulls and short hulls, designers use a displacement-to-length ratio. This is nothing more than a boat´s displacement in long tons (2240 lbs) divided by 1/100 her waterline in feet cubed (multiplied by itself three times), or:

• Displacement-to-length ratio (Disp/WL) = 2240/(WL ft./100)ˆ3
• Displacement-to-length ratio (Disp/WL) = 2240/(WL m/30.5)ˆ3

The ranges of Disp/WL ratio considered heavy or light have shifted some over the years. At present

• Under 50 is super ultralight
• 50 to 120 is ultralight;
• 121 to 250 is light
• 251 to 320 is medium
• 321 to 380 is heavy
• Over 380 is very heavy