Windsurfing Calculator
Estimate optimal windsurf sail, board volume, and fin size from rider weight and wind speed using J. Douglass formulas.
Windsurfing Calculator
This Windsurfing Calculator estimates the ideal sail size, board volume, and fin size based on your body weight and wind conditions. It uses the J. Douglass formulas widely used in the windsurfing community.
The Douglass Sail Size Formula
Sail size (m²) = (1.34 × rider weight in kg) / wind speed in knots. A heavier sailor or lighter wind requires a larger sail. The comfortable range spans roughly 15% below and above the ideal size.
Board Volume and Fin Size
Board volume is estimated from your weight plus a skill-based offset, beginners need more volume for stability, while advanced riders use less. Fin size is approximated as sail area multiplied by 30 cm².
Frequently Asked Questions
What size sail do I need for windsurfing?
Use the Douglass formula: multiply your weight in kg by 1.34, then divide by wind speed in knots. The calculator also shows a comfortable sail range.
How does skill level affect board volume?
Beginners need roughly 40 liters more than their body weight, while expert wave riders may use boards close to or below their body weight for maneuverability.
How do I find the right wind speed for my sail?
Switch to reverse mode and enter your sail size. The calculator computes ideal wind speed and a usable wind range using the same Douglass formula rearranged for wind.
How big should my fin be?
A common rule of thumb is fin area in cm² equals sail area in m² multiplied by 30. The calculator applies this automatically from your recommended sail size.
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