Use this nautical calculation for a transparent unit, speed, tide, rhumb-line, or apparent-to-true wind estimate when position, heading, current, and unit conventions are explicit.

Waterline length

Required number input.

Calculate the displacement hull speed in knots from the waterline length in feet. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Hull speed

The resulting hull speed returned as a number.

• Navigation results can depend on Earth model, chart datum, magnetic variation, leeway, current, wind reference, tide station, hull form, water depth, and weather. Simplified hull-speed and rhumb-line formulas do not establish a safe passage.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Cross-check current charts, tide and weather services, vessel instruments, and approved navigation methods before operational use.

• True Wind Speed Calculator

  Calculate the true wind speed in knots from apparent wind speed, apparent wind angle, and boat speed.

• Knots to Kilometers Per Hour Converter

  Convert a speed in knots to kilometers per hour using the exact factor of one point eight five two.

• Rhumb Line Distance Calculator

  Calculate the rhumb line distance in nautical miles between two geographic positions along a constant bearing.