Speed converter
Convert km/h, mph, knots, metres per second and feet per second. Exact factors, including the knot's nautical-mile definition.
Common speed conversions
Every speed unit
| Unit | Symbol | In metres per second |
|---|---|---|
| Metres per second | m/s | 1 |
| Kilometres per hour | km/h | 0.27777778 |
| Miles per hour | mph | 0.44704 |
| Feet per second | ft/s | 0.3048 |
| Knots | kn | 0.51444444 |
Questions
What is a knot?
One nautical mile per hour — and a nautical mile is one minute of latitude, fixed at exactly 1,852 metres. That is the whole point of it: a ship making 10 knots for six hours has covered one degree of latitude, which you can read straight off a chart without converting anything.
Why do sailors and pilots say "knots" and not "knots per hour"?
Because the "per hour" is already inside the word. A knot is a speed, not a distance, so "knots per hour" would be an acceleration. The name comes from the knotted rope once paid out behind a ship and counted against a sand glass.
What's the quick way to convert mph to km/h in my head?
Multiply by 1.6, or add 60%. For the other direction, take away a third and then a little more. Fifty mph is 80 km/h, 60 is 97, 70 is 113 — worth remembering if you drive across a border where the signs change.
Why isn't Mach on this page?
Because it is not a fixed unit. Mach 1 is the local speed of sound, which falls as air gets colder — around 1,235 km/h at sea level but closer to 1,062 km/h in the stratosphere where airliners cruise. A single conversion factor would be wrong nearly everywhere.