The Beaufort Wind Scale
The Beaufort Scale is the standard way of describing wind strength by its observed effects rather than by an instrument reading. It was devised in 1805 by Francis Beaufort — then a Royal Navy commander, later Rear Admiral Sir Francis Beaufort — who wanted a common, objective way for ships' officers to log wind strength without relying on an anemometer. His original scale judged wind purely by how much sail a man-of-war could safely carry, from "just sufficient to give steerage way" up to "that which no canvas sail could withstand". The Royal Navy adopted it formally once Beaufort became the Admiralty's Hydrographer in 1838, and it spread from there to merchant shipping and eventually to land use, where the numbers were redefined against the visible effect of wind on smoke, trees, and buildings instead of sails. The scale used today still runs 0 to 12, and it's this land/sea version, with modern wind-speed equivalents attached, that's shown below.
The Scale at a Glance
Colours match the full table below.
Full Reference Table
| Beaufort Number |
Description | Wind Speed | Wave Height | Sea Conditions | Land Conditions | |||
|---|---|---|---|---|---|---|---|---|
| mph | km/h | kts | m | ft | ||||
| 0 | Calm | < 1 | < 1 | < 1 | 0 | 0 | Flat | Calm. Smoke rises vertically |
| 1 | Light air | 1 - 3 | 1.1 - 5.5 | 1 - 2 | 0 - 0.2 | 0 - 1 | Ripples without crests | Wind motion visible in smoke |
| 2 | Light breeze | 4 - 7 | 5.6 - 11 | 3 - 6 | 0.2 - 0.5 | 1 - 2 | Small wavelets. Crests of glassy appearance, not breaking | Wind felt on exposed skin. Leaves rustle |
| 3 | Gentle breeze | 8 - 12 | 12 - 19 | 7 - 10 | 0.5 - 1 | 2 - 3.5 | Large wavelets. Crests begin to break; scattered whitecaps | Leaves and smaller twigs in constant motion |
| 4 | Moderate breeze | 13 - 17 | 20 - 28 | 11 - 15 | 1 - 2 | 3.5 - 6 | Small waves with breaking crests. Fairly frequent white horses | Dust and loose paper raised. Small branches begin to move |
| 5 | Fresh breeze | 18 - 24 | 29 - 38 | 16 - 20 | 2 - 3 | 6 - 9 | Moderate waves of some length. Many white horses. Small amounts of spray | Branches of a moderate size move. Small trees begin to sway |
| 6 | Strong breeze | 25 - 30 | 39 - 49 | 21 - 26 | 3 - 4 | 9 - 13 | Long waves begin to form. White foam crests are very frequent. Some airborne spray is present | Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult |
| 7 | Near gale | 31 - 38 | 50 - 61 | 27 - 33 | 4 - 5.5 | 13 - 19 | Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction | Whole trees in motion. Effort needed to walk against the wind |
| 8 | Gale | 39 - 46 | 62 - 74 | 34 - 40 | 5.5 - 7.5 | 17 - 21 | Moderately high waves with breaking crests forming spindrift. Well-marked foam streaks | Twigs break from trees. Cars veer on the road. Progress on foot seriously impeded |
| 9 | Strong gale | 47 - 54 | 75 - 88 | 41 - 47 | 7 - 10 | 23 - 32 | High waves whose crests sometimes roll over. Dense foam blown along wind direction | Some branches break off trees. Construction signs and barricades blow over |
| 10 | Storm | 55 - 63 | 89 - 102 | 48 - 55 | 9 - 12.5 | 29 - 41 | Very high waves with overhanging crests. Large patches of foam give the sea a white appearance | Trees broken off or uprooted. Poorly attached roof shingles peel off |
| 11 | Violent storm | 64 - 72 | 103 - 117 | 56 - 63 | 11.5 - 16 | 37 - 52 | Exceptionally high waves. Very large patches of foam cover much of the sea surface | Widespread damage to vegetation. Many roofing surfaces damaged |
| 12 | Hurricane | ≥ 73 | ≥ 118 | ≥ 64 | ≥ 14 | ≥ 46 | Huge waves. Sea completely white with foam and spray, greatly reducing visibility | Very widespread damage to vegetation. Windows may break; weak structures damaged |
Why It Still Matters on the Solent
Southampton sits on one of the busiest stretches of sailing water in the country, and the Beaufort Scale is still the language used in Met Office shipping and coastal forecasts for exactly the reason Beaufort designed it: what a sailor needs to know is what the wind will actually do to a boat, not just a number in mph. Force 4-5 is the top end of comfortable sailing for most small-boat crews, force 6 is when it starts being properly hard work, and gale warnings (force 8 and above) are issued specifically using these Beaufort force numbers, not raw wind speed. Our live wind speed reading on the home page dashboard can be cross-referenced against the table above to see what force the wind is blowing at right now.