Short answer: 1 knot = 1.15078 mph = 1.852 km/h = 0.514 m/s. To convert knots to mph, multiply by about 1.15. To convert knots to km/h, multiply by 1.85 (almost double). For m/s, halve it. The full chart below shows every common wind speed plus what it actually feels like.
Wind apps, marine forecasts, and aviation all speak in knots, while most weather apps and car speedometers use mph or km/h. So you end up doing mental math at the beach. We made this so you don’t have to. Below is one clean conversion table for the wind speeds you’ll actually meet, from a gentle 5 knots to a near-gale 40, with a column for what each one feels like and what you can do in it.
What is a knot, exactly?
A knot is one nautical mile per hour, and one nautical mile is 1.852 km, so 1 knot = 1.852 km/h = 1.15078 mph = 0.514 m/s. As NOAA explains, the nautical mile is tied to the Earth’s coordinates, with one nautical mile equaling one minute of latitude. The unit comes from old sailing ships that measured speed by counting knots on a rope payed out behind the boat over a fixed time.
The numbers above are the canonical conversions, not approximations. Keep them and you can move between any wind unit you’ll meet. The only one people get wrong is treating a knot like a regular mile, it’s about 15 percent faster.
The knots conversion chart (mph, km/h, m/s)
These are the wind speeds you’ll actually see on a forecast, with conversions to all three common units and what each one means on the water and on land. Beaufort bands and descriptions match our Beaufort scale in knots reference, so the numbers stay consistent across both pages.
| Knots | mph | km/h | m/s | Beaufort | What it feels like / what you can do |
|---|---|---|---|---|---|
| 5 | 5.8 | 9.3 | 2.6 | F2 light breeze | Leaves rustle, wavelets. Too light for most boards; foilers and light-wind kites only. |
| 10 | 11.5 | 18.5 | 5.1 | F3 gentle breeze | Twigs move, large wavelets. Beginner dinghy sailing, big kites, light wing days. |
| 15 | 17.3 | 27.8 | 7.7 | F4 moderate breeze | Small branches sway, frequent whitecaps. Solid all-round riding for most sports. |
| 20 | 23.0 | 37.0 | 10.3 | F5 fresh breeze | Small trees sway, many whitecaps. The sweet spot: all-around kite, fast dinghy sailing. |
| 25 | 28.8 | 46.3 | 12.9 | F6 strong breeze | Large branches move, foam crests. Powered up. Smaller kites and sails, reef the boat. |
| 30 | 34.5 | 55.6 | 15.4 | F7 near gale | Whole trees in motion, foam streaks. Experts on small gear only. Time to depower. |
| 35 | 40.3 | 64.8 | 18.0 | F8 gale | Twigs break off trees, breaking crests. Survival conditions for most. Stay in. |
| 40 | 46.0 | 74.1 | 20.6 | F8 gale | High waves, hard to walk into. Beyond almost everyone’s limit. Watch from shore. |
Numbers rounded to one decimal. Source: standard nautical conversions (1 kt = 1.852 km/h) and the Beaufort wind scale bands published by the US National Weather Service. For the full Force 0 to 12 scale, see our Beaufort chart.
How do you convert knots to mph in your head?
The fastest mental shortcut: add 15 percent. Knots times 1.15 lands within a hair of the true mph figure. So 20 knots is about 23 mph, and 30 knots is about 35 mph. For a rougher gut-check, just add half again: 20 plus 10 is 30, which overshoots a little but tells you the ballpark.
For km/h, almost double the knots (times 1.85). 20 knots is roughly 37 km/h, 30 knots is about 56 km/h. For m/s, halve the knots (times 0.514): 20 knots is around 10 m/s. These three shortcuts (×1.15, ×1.85, ÷2) cover every conversion you’ll need at the beach.
Set it once, skip the math. Download WindUp free and set your wind alarm in whatever unit you think in, knots, mph, km/h, or m/s. It rings the moment your spot hits your number, even on Do Not Disturb. No converting in your head at 6am.
Why do wind sports use knots?
Because one knot equals one nautical mile per hour, and one nautical mile equals one minute of latitude on any chart. That link between speed and the lines on a map made knots the standard for marine navigation centuries ago, and aviation followed. Today every serious wind forecast, from offshore sailing to paragliding, defaults to knots.
That’s why the WindUp app and most wind tools show knots first. If you sail, the unit matches your charts and your VHF forecast. Our sailing guide goes deeper on the wind ranges that suit each boat type, all in knots. You can switch any app to mph or km/h, but the wider community thinks in knots, so it pays to get fluent.
What does each wind speed actually feel like?
Numbers only mean something once you connect them to the water. 10 knots barely fills a big kite. 20 knots, a Force 5 fresh breeze, is where most sports come alive: small trees sway, the sea is dotted with whitecaps, and you’re fully powered on standard gear. By 30 knots (Force 7 near gale) whole trees move and only experts should be out.
The jump from 15 to 25 knots is the difference between “underpowered” and “overpowered” for most riders. That narrow band is exactly why a live alarm beats eyeballing a forecast: 18 knots and 24 knots feel like different sports, and a forecast that says “20ish” won’t tell you which one you’re getting. The live reading will.
FAQ
The questions we hear most: a knot is about 15 percent faster than a mph, almost double a km/h, and roughly half an m/s. Memorize 1 kt = 1.15 mph = 1.85 km/h = 0.51 m/s and you can convert any wind speed on the fly. For the force-by-force breakdown, the Beaufort chart has it. To stop converting entirely, set your alarm in your own unit and let WindUp ring you.
