Beaufort Scale Calculator

How it works

v (m/s) ≈ 0.836 · B^(3/2); B = (v ÷ 0.836)^(2/3) rounded; 1 kt = 0.5144 m/s, 1 mph = 0.447 m/s

Admiral Beaufort’s 1805 scale let sailors report wind by its visible effects before anemometers existed, and it survives in shipping forecasts and everyday language (“gale force 8”). The modern definition ties each force to a band of 10-minute mean wind speed at 10 m height through the empirical formula v = 0.836·B^1.5. Force 12 (hurricane force, 64+ knots) tops the scale; tropical cyclones are graded beyond it by the Saffir–Simpson categories.

Worked example

35 km/h (9.7 m/s) → (9.7/0.836)^(2/3) = 5.1 → force 5, a fresh breeze: small trees sway, moderate waves with many whitecaps.

Frequently asked questions