Marine Apparent Wind Calculator
Calculate apparent wind speed and an unsigned bow angle from true wind and boat speed in the same water-relative reference frame.
A QUICK WALKTHROUGH
How to use this tool
- Enter true wind and boat speeds in knots using the same water-relative frame.
- Enter the true wind angle from the bow from 0 to 180 degrees.
- Calculate speed and angle, then copy or download the report.
Formula and units
x = TWS × cos(θ) + boat speed; y = TWS × sin(θ). AWS = hypot(x,y); unsigned AWA = atan2(y,x) in degrees.
Scope
Angles are unsigned bow angles; 0° is from ahead and 180° from astern. Use one water-relative frame, not mixed ground and water speeds. The zero vector has no defined direction. No sail setting, weather, route or safety advice is provided.
Local processing
Inputs stay in your browser. The report includes inputs, formulas and scope.
GOOD TO KNOW
Common questions
What happens when the apparent wind vector is zero?
Speed is zero and the angle is undefined, because a zero vector has no direction.