The Beaufort scale describes wind force on a scale from 0 (calm) to 12 (hurricane), based on the observed effects of wind on the sea and on land. It is one of the most useful tools any sailor can know.
What is the Beaufort scale?
Devised in 1805 by Admiral Francis Beaufort, the scale links a wind-force number to a description and a wind-speed range. It lets sailors estimate conditions at a glance, without instruments.
The Beaufort wind force table (0–12)
- 0 – Calm: under 1 knot; the sea is mirror-smooth.
- 3 – Gentle breeze: 7–10 knots; large wavelets, ideal easy sailing.
- 5 – Fresh breeze: 17–21 knots; moderate waves, lively sailing.
- 7 – Near gale: 28–33 knots; sea heaps up, demanding conditions.
- 9 – Strong gale: 41–47 knots; high waves, only for experienced crews.
- 12 – Hurricane: 64+ knots; the sea is completely white.
What wind force can you sail in?
Most crews enjoy sailing best in Force 3–4 (about 7–16 knots). From Force 6 upwards conditions become demanding; beginners should stay in harbour or sail only with an experienced skipper.
Frequently asked questions
How many levels does the Beaufort scale have?
Thirteen, from 0 (calm) to 12 (hurricane).
How do you convert Beaufort to knots?
Each force covers a wind-speed range – for example Force 5 is about 17–21 knots. Use the table above as a quick reference.
Want to learn to read the wind on the water? Discover our skipper training.
