Beaufort Scale Calculator
Enter the wind speed in knots to find its Beaufort force, the standard sea-state description and the typical wave height you can expect.
How to read the Beaufort scale
- Enter the sustained wind speed in knots.
- Read the Beaufort force number from 0 to 12.
- See the matching sea-state description and the typical wave height.
Examples
A 25 knot wind
windSpeedKnots = 25
Force 6, strong breeze, typical wave height about 3 m
Frequently asked questions
What is the Beaufort scale?
It is a 0 to 12 scale that links wind speed to the look of the sea and land. Force 0 is dead calm and force 12 is hurricane-force wind with towering seas.
What wind speed is a gale?
A gale is force 8, which is 34 to 40 knots of sustained wind. Force 7 (28 to 33 knots) is a near gale and force 9 (41 to 47 knots) is a strong gale.
Are the wave heights exact?
No. The wave heights are typical open-sea values for fully developed seas. Real waves depend on how long and how far the wind has blown, plus depth and current.
Should I use gusts or sustained wind?
The Beaufort scale is based on sustained wind speed, usually a 10 minute average. Gusts are higher and brief, so judge conditions on the steady wind.
How do I convert from mph or km/h?
Divide miles per hour by about 1.151, or kilometres per hour by 1.852, to get knots first, then read off the force.
Related tools
Hull Speed Calculator
Calculate the theoretical hull speed of a displacement boat from its waterline length. Get the result in knots, mph and km/h with the formula shown.
Anchor Scope Calculator
Calculate how much anchor rode to let out from water depth, bow height, scope ratio and tide. Get the total height and rode length in feet with the formula.
Sail Area to Displacement
Calculate a sailboat's sail area to displacement (SA/D) ratio from sail area and weight. See the ratio, the displacement volume and a performance band.
Boat Fuel Calculator
Estimate trip fuel for a powerboat from distance, speed, gallons per hour and a safety reserve. See hours underway and base and total fuel in gallons.
Distance to Horizon Calculator
Calculate how far away the horizon is from your eye height. Get the distance in nautical miles, statute miles and kilometres with the formula shown.