This estimator can be used to predict power required and range of a displacement vessel. It looses accuracy above speed length ratios of about 1.6 and in displacement below about 6 Long Tons. The formulae used to build this estimator are derived from Robert Beebe's book, "Voyaging under Power". This estimetor is gives results that are only approximations. To get the actual values for any vessel requires measurement of that vessel's performance.