Support for WindCalc App

As questions arise, they will be posted in the WindCalc FAQ
You can submit questions and get support at [email protected]
or call 206-783-1414

WindCalc is a free app for computers and mobile devices that converts between true and apparent wind observations. Copies are available at

Windows PC version

Mac Version

iOS version

Android version

To Find True Wind

(1) In the top vessel section, enter the vessel speed (SPD) and heading (HDG), and check the side of the vessel the wind is on.

(2) In the apparent wind section, enter the AWS and AWA

(3) Press the Compute True Wind button.

(4) That will find the TWS, TWA, and also apply the TWA to the Heading to get the true wind direction (TWD)

If you want to compute the true wind that is used by meteorologists and numerical weather model forecasts, then use SPD = SOG and HDG = COG. This will then compute the true wind relative to the fixed ground.

The wind computed using SOG and COG is sometimes called "ground wind" by sailors who wish to distinguish it from the name "true wind" used in polar diagrams. The "true wind" referenced in polar diagrams is relative to the water, which might be moving due to notable current.

To compute true wind for use with polar diagram and target speed tables, use SPD = STW (speed through water, relative to the water) and HDG = CTW (course through water.)

This distinction between "ground wind" and "true wind" is only important when sailing in notable current.

To Find Apparent Wind

(1) In the top vessel section, enter the vessel speed (SPD) and heading (HDG), and check the side of the vessel the wind is on.

(2) In the true wind section, enter the TWS and TWA

(3) Press the Compute Apparent Wind button.

(4) That will find the AWS, AWA, and also apply the AWA to the Heading to get the apparent wind direction (AWD)

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