Wind speed converter
Type a wind speed in any unit and read the rest — knots, metres per second, km/h, mph and the matching Beaufort force. Runs entirely in your browser.
Force 4, moderate breeze: Small waves becoming longer, fairly frequent white horses. Probable open-sea wave height around 1 m.
Quick reference
| Knots | m/s | km/h | mph | Beaufort |
|---|---|---|---|---|
| 5 | 2.6 | 9.3 | 5.8 | 2 (Light breeze) |
| 10 | 5.1 | 19 | 12 | 3 (Gentle breeze) |
| 12 | 6.2 | 22 | 14 | 4 (Moderate breeze) |
| 15 | 7.7 | 28 | 17 | 4 (Moderate breeze) |
| 18 | 9.3 | 33 | 21 | 5 (Fresh breeze) |
| 20 | 10 | 37 | 23 | 5 (Fresh breeze) |
| 25 | 13 | 46 | 29 | 6 (Strong breeze) |
| 30 | 15 | 56 | 35 | 7 (Near gale) |
| 35 | 18 | 65 | 40 | 8 (Gale) |
| 40 | 21 | 74 | 46 | 8 (Gale) |
Exact factors: 1 kt = 1.852 km/h = 0.5144 m/s = 1.1508 mph. A knot is one nautical mile per hour.
The Beaufort scale
The World Meteorological Organization's scale, as used in marine forecasts. Wave heights are probable open-sea values — coastal water with short fetch runs lower.
| Force | Name | Knots | Waves | At sea |
|---|---|---|---|---|
| 0 | Calm | <1 | 0 m | Sea like a mirror. |
| 1 | Light air | 1–3 | 0.1 m | Ripples with the appearance of scales, no foam crests. |
| 2 | Light breeze | 4–6 | 0.2 m | Small wavelets, glassy crests that do not break. |
| 3 | Gentle breeze | 7–10 | 0.6 m | Large wavelets, crests begin to break, scattered white horses. |
| 4 | Moderate breeze | 11–16 | 1 m | Small waves becoming longer, fairly frequent white horses. |
| 5 | Fresh breeze | 17–21 | 2 m | Moderate waves taking longer form, many white horses, some spray. |
| 6 | Strong breeze | 22–27 | 3 m | Large waves form, extensive white foam crests, probably some spray. |
| 7 | Near gale | 28–33 | 4 m | Sea heaps up, white foam from breaking waves blown in streaks. |
| 8 | Gale | 34–40 | 5.5 m | Moderately high waves, crests break into spindrift, foam in well-marked streaks. |
| 9 | Strong gale | 41–47 | 7 m | High waves, dense foam streaks, crests begin to topple and roll over, spray may reduce visibility. |
| 10 | Storm | 48–55 | 9 m | Very high waves with long overhanging crests, sea surface takes on a white appearance, visibility affected. |
| 11 | Violent storm | 56–63 | 11.5 m | Exceptionally high waves, sea completely covered with long white patches of foam, visibility affected. |
| 12 | Hurricane force | 64+ | 14+ m | Air filled with foam and spray, sea completely white with driving spray, visibility very seriously affected. |
Common questions
How many km/h is one knot?
One knot is exactly 1.852 km/h — a knot is one nautical mile (1,852 m) per hour. It's also 0.514 m/s and about 1.151 mph.
How do I convert m/s to knots quickly in my head?
Double the m/s value and take off 3%: 10 m/s ≈ 19.4 kt, so "double it" (20) gets you close enough on the water. The exact factor is 1.944.
What wind speed do I need to kitesurf or windsurf?
Most kitesurfers ride from about 12 knots (Beaufort 4) with a big kite; windsurfers start planing around 12–15 knots. 15–25 knots (force 4–6) is the sweet spot for both sports.
Is the Beaufort scale about wind speed or sea state?
Both — each Beaufort force is defined by a wind-speed band (in knots) and describes the sea state that wind typically produces in open water. Near the coast, with limited fetch, waves stay smaller than the table suggests.
Now check what's actually blowing on the coast.
WindNow shows live wind speed, gusts and direction from real coastal weather stations across France, Croatia and Slovenia — minutes old, not a forecast.
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