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 of the vessel.

Length overall (ft)

Length overall; leave at zero to assume it equals waterline length.

Waterline length (ft)

Waterline length.

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

Comfort ratio

Comfort ratio; larger values indicate a steadier, heavier 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.

• Displacement Length Ratio Calculator

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

• Helm Balance Ratio

  Express the signed longitudinal separation between sail-plan center of effort and center of lateral resistance as a percentage of length overall.

• Anchor Circle Radius Calculator

  Estimate the maximum anchor-to-bow radius from water depth and rode scope. Add the vessel length when checking the full area swept by the stern.