| Beaufort number !! Wind speed at 10 m above sea level (knots / km/h) !! Description !! Wave height (m) !! Sea conditions !! Land conditions |
| 0 | less than 1 / 2 | Calm | 0 | Flat. | Calm. |
| 1 | 2 / 4 | Light air | 0.1 | Ripples without crests. | Wind motion visible in smoke. |
| 2 | 5 / 9 | Light breeze | 0.2 | Small wavelets. | Wind felt on exposed skin. Leaves rustle. |
| 3 | 9 / 17 | Gentle breeze | 0.6 | Large wavelets. | Leaves and smaller twigs in constant motion. |
| 4 | 13 / 24 | Moderate breeze | 1 | Small waves. | Dust and loose paper raised. Small branches begin to move. |
| 5 | 19 / 35 | Fresh breeze | 2 | Moderate (1.2 m) longer waves. Some foam and spray. | Smaller trees sway. |
| 6 | 24 / 44 | Strong breeze | 3 | Large waves with foam crests and some spray. | Large branches in motion. Umbrella use becomes difficult. |
| 7 | 30 / 56 | Near gale | 4 | Sea heaps up and foam begins to streak. | Whole trees in motion. Effort to walk against the wind. |
| 8 | 37 / 68 | Gale | 5.5 | Moderately high waves with breaking crests forming spindrift. Streaks of foam. | Twigs broken from trees. |
| 9 | 44 / 81 | Severe gale | 7 | High waves (2.75 m) with dense foam. Wave crests start to roll over. Considerable spray. | Light structure damage. |
| 10 | 52 / 96 | Storm | 9 | Very high waves. the sea surface is white and there is considerable tumbling. Visibility is reduced. | Trees uprooted. Considerable structural damage. |
| 11 | 60 / 111 | Violent storm | 11.5 | Exceptionally high waves. | Widespread structural damage. |
| 12 | 64 / 118 and higher | Hurricane | 14+ | Huge waves. Air filled with foam and spray. Sea completely white with driving spray. Visibility very greatly reduced. | Massive and widespread damage to structures. |
The scale was created by the Irish naval commander Sir