| Beaufort number |
Designation | Physical effects (on land) | Pressure lbs. per sq. ft. |
Meters per second (Br.) |
Miles per hour | |
| Br. | U.S. | |||||
| 0 | Calm | Calm; smoke rises vertically | 0 | Less than 0.3 |
Less than 1 |
0-3 |
| 1 | Light air | Direction of wind shown by smoke drift, but not by wind vanes | .01 | 0.3-1.5 | 1-3 | 3-8 |
| 2 | Slight breeze | Wind felt on the face; leaves rustle; ordinary vane moved by wind | .08 | 1.6-3.3 | 4-7 | 8-13 |
| 3 | Gentle breeze | Leaves and small twigs in constant motion; wind extends light flag | .28 | 3.4-5.4 | 8-12 | 13-18 |
| 4 | Moderate breeze | Raises dust; small branches are moved | .67 | 5.5-7.9 | 13-18 | 18-23 |
| 5 | Fresh breeze | Small trees in leaf begin to sway; crsted wavelets form on inland waters | 1.31 | 8.0-10.7 | 19-24 | 23-28 |
| 6 | Strong breeze | Large branches in motion; umbrellas used with difficulty | 2.3 | 10.8-13.8 | 25-31 | 28-34 |
| 7 | Moderate gale | Whole trees in motion, inconvenience felt when walking against the wind | 3.6 | 13.9-17.1 | 32-38 | 34-40 |
| 8 | Fresh gale | Breaks twigs off trees; impedes progress | 5.4 | 17.2-20.7 | 39-46 | 40-48 |
| 9 | Strong gale | Slight structural damage occurs (chimney pots and slates removed) | 7.7 | 20.8-24.4 | 47-54 | 48-56 |
| 10 | Whole gale | Seldom experienced inland; trees uprotted; considerable structural damage occurs | 10.5 | 24.5-28.4 | 55-63 | 56-62 |
| 11 | Storm | Very rarely experienced; accompanied by widespread damage | 14.0 | 28.5-33.5 | 64-75 | 65-75 |
| 12 | Hurricane | Above 17.0 |
Above 33.6 |
Above 75 |
Over 75 | |
Millibar pressures are approximately one-half as great as pound per square inch pressures.
