Wind Speed Converter: km/h, mph, m/s, Knots and Beaufort
Enter a wind speed in any unit. The other units and the Beaufort force update as you type, which makes it quick to compare a forecast in km/h with a marine report in knots.
Formula
- 1 km/h = 1000 / 3600 m/s ≈ 0.27778 m/s
- 1 mph = 0.44704 m/s (exact, from the international mile of 1609.344 m)
- 1 knot = 1852 / 3600 m/s ≈ 0.51444 m/s (one nautical mile per hour)
Speeds are rounded to 2 decimal places for display. The Beaufort force is taken from the WMO metre-per-second table after rounding the speed to 0.1 m/s, the precision that table is published at.
Reference table
| Force | Description | m/s | km/h | mph | knots |
|---|---|---|---|---|---|
| 0 | Calm | 0–0.2 | 0–0.7 | 0–0.4 | 0–0.4 |
| 1 | Light air | 0.3–1.5 | 1.1–5.4 | 0.7–3.4 | 0.6–2.9 |
| 2 | Light breeze | 1.6–3.3 | 5.8–11.9 | 3.6–7.4 | 3.1–6.4 |
| 3 | Gentle breeze | 3.4–5.4 | 12.2–19.4 | 7.6–12.1 | 6.6–10.5 |
| 4 | Moderate breeze | 5.5–7.9 | 19.8–28.4 | 12.3–17.7 | 10.7–15.4 |
| 5 | Fresh breeze | 8–10.7 | 28.8–38.5 | 17.9–23.9 | 15.6–20.8 |
| 6 | Strong breeze | 10.8–13.8 | 38.9–49.7 | 24.2–30.9 | 21–26.8 |
| 7 | Near gale | 13.9–17.1 | 50–61.6 | 31.1–38.3 | 27–33.2 |
| 8 | Gale | 17.2–20.7 | 61.9–74.5 | 38.5–46.3 | 33.4–40.2 |
| 9 | Strong gale | 20.8–24.4 | 74.9–87.8 | 46.5–54.6 | 40.4–47.4 |
| 10 | Storm | 24.5–28.4 | 88.2–102.2 | 54.8–63.5 | 47.6–55.2 |
| 11 | Violent storm | 28.5–32.6 | 102.6–117.4 | 63.8–72.9 | 55.4–63.4 |
| 12 | Hurricane force | 32.7+ | 117.7+ | 73.1+ | 63.6+ |
Good to know
- The Beaufort scale describes the average wind over about 10 minutes at 10 m above the ground. Gusts are stronger than that average, so a gust speed can land in a higher band than the sustained wind it belongs to.
- The knot ranges above are converted from the WMO metre-per-second table, so their edges can differ by one knot from charts that publish separate knot bounds.