Apparent Wind Calculator

Apparent Wind Calculator

What your sails actually respond to isn't true wind - it's apparent wind, the vector combination of true wind and the wind created by your own boat's forward motion.

Apparent Wind = True Wind Vector + Boat's Own Motion Vector (added as vectors, not simple subtraction)

Example

15 knots true wind at 60┬░ from the bow, boat moving at 6 knots:

Apparent Wind: 18.7 knots at 43.9┬░ from the bow

The Bicycle Analogy

This is similar to how riding a bicycle on a perfectly still day still creates a headwind purely from your own forward movement through the air - a sailboat experiences the same effect, but combined with whatever true wind is actually blowing, not just calm air.

Why This Matters for Sail Trim

Apparent wind is always angled further forward and typically stronger than true wind when sailing upwind - understanding this relationship is essential for sailors to trim sails correctly (sails respond to apparent wind, not true wind) and to accurately read true wind conditions from onboard wind instruments, which typically display apparent wind directly and require this vector correction to determine actual true wind.