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.

Displacement (lb)

Displacement in pounds.

Waterline length (ft)

Waterline length.

Compute the displacement-to-length ratio; below two hundred is light, above three hundred is heavy. 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]

D/L ratio

D/L ratio; under two hundred is light, over three hundred is heavy.

• 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.

• Comfort Ratio Calculator

  Compute Ted Brewer's motion-comfort ratio from displacement, waterline length, and length overall. When LOA is omitted, it is assumed equal to LWL.

• Sail Area Displacement Ratio Calculator

  Compute the sail area to displacement ratio; above fifteen indicates good light-air performance.

• Ceiling Category Lookup

  Classify a cloud ceiling as low below five hundred feet, marginal below three thousand feet, or otherwise fine for visual flying rules.