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Speed is measured differently depending on context and country: km/h on most road signs, mph in the US and UK, m/s in physics, and knots at sea and in the air. Converting between them is a constant need for driving abroad, science homework, sailing or aviation.
Enter a value, pick the units, and the converted speed appears at once.
How is it calculated?
Key conversion factors
| Conversion | Factor |
|---|---|
| 1 m/s | 3.6 km/h |
| 1 mph | 1.609344 km/h |
| 1 knot | 1.852 km/h |
| 1 km/h | 0.621371 mph |
| 1 ft/s | 0.3048 m/s |
All speeds share one base — metres per second — so the tool converts to m/s and back to your target unit.
Where each unit is used
- km/h: road speed in most of the world.
- mph: road speed in the US and UK.
- m/s: the SI unit, used in physics and engineering.
- knots: one nautical mile per hour, used in maritime and aviation navigation.
- ft/s: occasional US engineering and ballistics contexts.
Quick estimates
- mph → km/h: multiply by 1.6 (60 mph ≈ 96 km/h).
- km/h → mph: multiply by 0.62 (100 km/h ≈ 62 mph).
- A knot is very close to 1.15 mph.
Where it helps
- Reading a foreign speed limit in your own units
- Physics problems that mix m/s and km/h
- Understanding wind or vessel speed in knots
Worked example
You're driving abroad and the limit reads 100 km/h, but your speedometer is in mph. Converting: 100 × 0.621371 = 62.14 mph. Going the other way, a 60 mph US limit is 60 × 1.609344 = 96.56 km/h. For a maritime example, a vessel doing 20 knots is travelling 20 × 1.852 = 37.04 km/h — a knot being one nautical mile per hour. The quick shortcut "km/h × 0.62 ≈ mph" gets you 62 for a fast sanity check, with the converter giving the exact 62.14.
FAQ
How do I convert km/h to mph?+
Multiply by 0.621371: 100 km/h × 0.621371 = 62.14 mph. For a quick estimate, multiply by 0.62. The tool handles every unit combination.
How do I convert mph to km/h?+
Multiply by 1.609344: 60 mph = 96.56 km/h. A rough estimate is mph × 1.6. Just pick the units and enter the value.
What is a knot?+
A knot is one nautical mile per hour, equal to 1.852 km/h (about 1.15 mph). It's used in maritime and aviation navigation because it ties neatly to latitude.
How do I convert m/s to km/h?+
Multiply by 3.6: 10 m/s = 36 km/h. Metres per second is the SI unit, so the converter uses it as the base for all speed conversions.
What is 100 km/h in mph?+
62.14 mph. That's a common motorway/highway speed, which is why the ~62 mph figure is worth remembering when driving between metric and imperial countries.
Why do ships and planes use knots?+
One knot is one nautical mile per hour, and a nautical mile is defined by the Earth's geometry (one minute of latitude), which makes navigation calculations simpler.