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.

Course (°)

Required number input.

True wind from (°)

Direction from which the true wind is blowing.

Calculate the corresponding course on the opposite tack by reflecting the current course across the true-wind direction. 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]

Opposite tack course (°)

The resulting opposite tack course 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.

• Opposite Tack Layline Bearing

  Calculate the bearing of the opposite tack layline by offsetting the true wind direction by the tacking angle to the chosen side of the wind.

• Lee Bow Effect Calculator

  Project current onto the desired course as current speed times the cosine of the relative angle. This along-course proxy does not model the true lee-bow effect, which also depends on heading, boat speed, and apparent wind.

• EP With Leeway

  Estimate the course made good by applying leeway to the true heading, subtracting the leeway angle on the starboard tack and adding it on the port tack.