Wind Triangle (E6B) Calculator

The calculator derives WCA from sin(WCA) = (wind speed × sin(wind angle)) ÷ TAS, and the sign of the result tells you which way to crab. A positive WCA means you need to crab right (point the nose right of your true course) to stay on track, while a negative WCA means crab left — the sign simply follows from which side of your course the wind is blowing across.

The wind-triangle trigonometry — sin(WCA) = (wind speed × sin(wind angle)) ÷ TAS and GS = TAS × cos(WCA) − headwind — only holds when the airspeed figure represents your actual speed through the air mass, which is what true airspeed is. Indicated airspeed reads low at altitude due to air density changes, so plugging IAS in directly would understate your speed through the air and throw off both the WCA and ground speed results; convert IAS to TAS first using the True Airspeed calculator.

Ground speed is TAS × cos(WCA) minus the headwind component. The cos(WCA) term accounts for the fact that once you crab into the wind, your nose isn't pointed exactly along your course, so only part of your true airspeed actually contributes to progress along the ground track; subtracting the headwind component then layers in the direct speed-reducing (or speed-adding, for a tailwind) effect of the wind itself.

This calculator works entirely in true degrees — true course and true wind direction — because that's how winds-aloft forecasts (FDs) report wind. METAR and ATIS surface wind reports, however, are given in magnetic degrees. Feeding a magnetic wind direction in without correcting for the local magnetic variation will shift the computed Wind Correction Angle and True Heading by exactly that variation amount.