The Beaufort scale: wind forces and their speeds
The Beaufort scale ranks wind in 13 forces, from 0 (calm) to 12 (hurricane force). A 50 km/h wind, about 27 knots, is force 6.
Updated November 7, 2026 · Sources
Forces defined in knots
Weather services define each force by a range of wind speeds in knots. The limits below are those of the UK Met Office, identical to NOAA's for the 13 forces.
A knot is one nautical mile per hour, exactly 1.852 km/h. The km/h and mph columns are converted from the knot limits, as in our calculator.
Beaufort scale table
A wind belongs to a force when its speed, rounded to the knot, falls within the range. From 64 knots, it is always force 12.
| Force | Knots | km/h | mph |
|---|---|---|---|
| 0 | 0 – 0 | 0 – 0 | 0 – 0 |
| 1 | 1 – 3 | 2 – 6 | 1 – 3 |
| 2 | 4 – 6 | 7 – 11 | 5 – 7 |
| 3 | 7 – 10 | 13 – 19 | 8 – 12 |
| 4 | 11 – 16 | 20 – 30 | 13 – 18 |
| 5 | 17 – 21 | 31 – 39 | 20 – 24 |
| 6 | 22 – 27 | 41 – 50 | 25 – 31 |
| 7 | 28 – 33 | 52 – 61 | 32 – 38 |
| 8 | 34 – 40 | 63 – 74 | 39 – 46 |
| 9 | 41 – 47 | 76 – 87 | 47 – 54 |
| 10 | 48 – 55 | 89 – 102 | 55 – 63 |
| 11 | 56 – 63 | 104 – 117 | 64 – 72 |
| 12 | ≥ 64 | ≥ 119 | ≥ 74 |
How to use it
- Convert the wind speed to knots and round it: the row it falls in gives the force.
- Forecasts for sailors and coasts often give the wind as a force rather than a speed.
- Gusts are short peaks above the average wind: the force describes the average wind.