Convert between meters per second, kilometers per hour, miles per hour, feet per second and knots. Useful for driving, sailing, weather reports, and sports statistics.
Quick reference
- 100 km/h = 62.1371 mph
- 60 mph = 96.5606 km/h
- 1 m/s = 3.6 km/h
- 1 knot = 1.852 km/h = 1.15078 mph
Speed limits, weather reports, and sailing all use different speed units depending on the country — km/h is standard almost everywhere except the US and UK, which use mph, and knots are standard at sea and in aviation.
How to convert speed units
Speed conversions follow from distance and time. One kilometer per hour is 1,000 m ÷ 3,600 s, so to convert m/s to km/h you multiply by 3.6. One mile per hour is 1.609344 km/h, and one knot (one nautical mile per hour) is exactly 1.852 km/h.
Example: a 120 km/h speed limit is 120 ÷ 1.609344 = 74.56 mph.
Frequently asked questions
How do I quickly convert km/h to mph?
Multiply by 0.6 for a rough answer (or by 5/8 for a closer one). 100 km/h is about 62 mph.
Why are knots used at sea and in the air?
A nautical mile matches one minute of latitude on the Earth’s surface, which makes distance and speed calculations on charts straightforward. A knot is one nautical mile per hour.
What is the speed of sound?
At sea level and 20°C, sound travels at about 343 m/s, which is roughly 1,235 km/h or 767 mph.