Hull speed, also known as displacement speed, is a rule of thumb to estimate the maximum speed a displacement hull can efficiently travel through water. It is primarily based on the length of the boat's waterline (the length of the hull at the water's surface). This concept originates from the observation that the speed of the wave created by the boat starts to limit the boat's speed once the wave's length is equal to the waterline length of the boat.

• [-5] : slow

• [5-] : fast