Use this sailing calculation as a planning or educational cross-check for navigation, wind and current, rig loads, stability, anchoring, tides, visibility, performance, or recovery under explicitly stated conditions.

Friction coefficient

Friction (skin drag) coefficient between 0.001 and 0.01.

Speed (m/s)

Boat speed through the water.

Wetted area (m²)

Wetted surface area of the hull.

Compute frictional hull resistance using frictionalResistanceNewtons = 0.5 * 1025 * speedMs^2 * wettedAreaM2 * frictionCoefficient with a default coefficient of 0.004. 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]

Frictional resistance (N)

Frictional resistance opposing forward motion.

• Actual conditions change with vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, regulations, and safety margins. Simplified formulas do not replace seamanship, approved stability data, or current navigation information.
• 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 official charts, tide and weather services, instrument data, vessel manuals, and collision regulations; maintain conservative margins and a safe alternative plan.

• Wetted Surface Estimate

  Estimate wetted surface from displacement using wettedSurfaceAreaM2 = displacementTonnes^(2/3) * wettedCoefficient with a default coefficient of 2.5.

• Wave Making Resistance Ratio

  Compute the wave making share of total hull resistance using wavemakingRatioPercent = waveResistanceNewtons / totalResistanceNewtons * 100.

• Air Draft With Heel

  Estimate effective air draft while heeled using a simplified rotation about the lower rail. Actual clearance also depends on hull geometry, trim, waves, and the heel pivot.