Speed Converter (km/h, mph, knots)
Kilometres per hour to miles per hour, knots and metres per second — exact, as you type.
Fast, easy and free — your answer appears as you type, and whatever you enter stays on your device.
Convert between km/h, mph, knots, metres per second and feet per second as you type. The factors are exact — 1 mph is precisely 0.44704 m/s — and the one used is shown under the answer.
How to use it
- Pick your unitskm/h to mph for driving, knots for boats and weather, m/s for science and sprinting.
- Type the speedThe answer appears instantly; Swap reverses the direction.
- Check the factorThe exact multiplier is printed beneath the result.
Three worlds, three units
Speed has settled into three camps. Roads use km/h in most of the world and mph in the US and UK. Sea and air use knots, because a nautical mile matches a minute of latitude and keeps navigation arithmetic honest. Science and sport use metres per second, the SI unit. Crossing between the camps is where this converter earns its keep — a rental car abroad, a marine forecast, a physics problem.
The anchors worth knowing: 100 km/h ≈ 62 mph ≈ 54 knots ≈ 27.8 m/s. Motorway speeds sit around 120 km/h / 75 mph; a walking pace is 5 km/h / 3.1 mph; a strong gale in a forecast (41–47 knots) is 76–87 km/h.
Wind speeds and forecasts
Weather is the sneaky one: forecasts mix units by country and by audience. Marine and aviation forecasts use knots, most European public forecasts use m/s, and US forecasts use mph. The same 20 m/s wind is 39 knots, 45 mph and 72 km/h — identical weather, four different-sounding numbers. When a storm report seems wildly different from what you expected, check the unit before doubting the forecast.
The speeding-ticket margin
A practical note for driving abroad: the numeric gap between km/h and mph is large enough to matter. 80 on a UK sign means 80 mph on a motorway — 129 km/h — while 80 on a French sign means 80 km/h, barely 50 mph. Rental-car speedometers usually show both scales, but GPS apps follow the phone's settings, not the country. Two seconds with a converter beats a fine in the post.
Whatever you enter stays on your device, and the tool keeps working offline once loaded.
Questions people ask
How do I convert km/h to mph quickly in my head?
Multiply by 0.6 for a good estimate: 100 km/h is about 60 mph (exactly 62.14). Going the other way, add 60%: 70 mph is about 112 km/h (exactly 112.65). The estimate errs safe — it slightly understates the mph figure.
What is a knot?
One nautical mile per hour — exactly 1.852 km/h. Ships and aircraft use knots because a nautical mile is one minute of latitude, which makes speed and chart distance line up directly. Wind speeds in marine forecasts are knots too.
Why do scientists use metres per second?
It is the SI unit, and it makes physics arithmetic clean: distance in metres divided by time in seconds, no conversion constants. For intuition, 1 m/s is a walk, 3 m/s a jog, 10 m/s is elite sprinting — Usain Bolt averaged 10.44 m/s over his 100 m world record.
How fast is Mach 1?
About 343 m/s (1,235 km/h) in air at 20°C — but it varies with temperature and altitude, which is why this converter does not offer Mach as a fixed unit. At cruising altitude it is closer to 1,062 km/h.
What speed is a minutes-per-km running pace?
Pace is the inverse of speed, so it needs a division, not a factor: 5:00 min/km is 12 km/h, 6:00 min/km is 10 km/h. Divide 60 by the pace in minutes to get km/h.
Are the conversions exact?
Yes. The mile is exactly 1,609.344 m and the nautical mile exactly 1,852 m, so every factor here is a definition, not an approximation. Only the display is rounded.