The scale from 0 to 12 that describes wind strength by its effects, from calm to hurricane force.
The Beaufort scale describes wind strength in 13 steps, from force 0 (calm) to force 12 (hurricane). It was devised in 1805 by the British naval officer Francis Beaufort, originally by what a sailing warship could carry, and later linked to measured wind speeds. Marine forecasts and many logbooks still give wind in Beaufort.
The scale
| Force | Description | Knots |
|---|---|---|
| 0 | Calm | < 1 |
| 1 | Light air | 1–3 |
| 2 | Light breeze | 4–6 |
| 3 | Gentle breeze | 7–10 |
| 4 | Moderate breeze | 11–16 |
| 5 | Fresh breeze | 17–21 |
| 6 | Strong breeze | 22–27 |
| 7 | Near gale | 28–33 |
| 8 | Gale | 34–40 |
| 9 | Strong gale | 41–47 |
| 10 | Storm | 48–55 |
| 11 | Violent storm | 56–63 |
| 12 | Hurricane force | ≥ 64 |
Good to know
- The values are averages over ten minutes at 10 m height. Gusts can be one or two forces stronger and are forecast separately.
- The apparent wind on board is not the Beaufort force: upwind it reads higher, downwind lower. Use the true wind.
- From force 6 onward, many coastal forecasts issue strong-wind warnings.
More in the guide to the Beaufort scale.
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