Speed Converter — mph, km/h, m/s, knots & feet per second

How it works

Speed is a length divided by a time, so its conversion factors come from the exact length definitions (NIST SP 811):

• 1 mile per hour = 1609.344 m ÷ 3600 s = 0.44704 m/s (exact).
• 1 km/h = 1000 ÷ 3600 = 0.2778 m/s, so 1 mph ≈ 1.609 km/h.
• 1 knot = 1 nautical mile per hour = 1852 m ÷ 3600 s ≈ 0.5144 m/s = 1.852 km/h — used in aviation and at sea.
• 1 foot per second = 0.3048 m/s.

The calculator converts your value to the base unit (metres per second) and then to the unit you want, so km/h↔mph, knot↔km/h and every other pairing use the same factors.

Worked example

Converting 100 km/h to mph:

100 km/h × (1000 ÷ 1609.344) = 62.1371 mph

Going the other way, 60 mph ≈ 96.56 km/h, and 1 knot = 1.852 km/h.

Frequently asked questions

How do you convert km/h to mph?

Multiply km/h by about 0.621371 (or divide by 1.609344), since 1 mile is 1.609344 km. So 100 km/h is about 62.14 mph.

How do you convert mph to km/h?

Multiply mph by 1.609344. So 60 mph is 60 × 1.609344 ≈ 96.56 km/h.

What is a knot?

A knot is one nautical mile per hour. Since a nautical mile is exactly 1852 meters, 1 knot is 1.852 km/h, or about 1.151 mph. It is standard for ships and aircraft.

How do you convert m/s to km/h?

Multiply meters per second by 3.6, since there are 3600 seconds in an hour and 1000 meters in a kilometer. So 10 m/s is 36 km/h.

How fast is 60 mph in feet per second?

About 88 ft/s. Since 1 mph = 0.44704 m/s and 1 foot = 0.3048 m, 60 mph works out to 88 feet per second — a handy figure in physics problems.

Are these conversions exact?

Yes. They derive from the exact definitions of the mile (1609.344 m), foot (0.3048 m) and nautical mile (1852 m), with the hour as 3600 seconds; only the displayed result is rounded.