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.

Current speed (kt)

Required number input.

Hours on course (h)

Required number input.

Calculate the distance gained or lost to the current along the course, with a favorable set positive and an adverse set negative. 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]

Gain or loss (nm)

The resulting gain or loss returned as a number.

• 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.

• Course Over Ground Calculator

  Calculate the resulting course over ground from vessel motion combined with current set and drift.

• Distance to Layline Calculator

  Calculate the distance along the course centerline to a layline from the lateral offset and half of the total angle between port and starboard tacks.

• Tide Gate Window Calculator

  Calculate the hours needed to transit a tidal gate against an adverse current from the gate distance, boat speed, and current strength.