Speed Converter

Includes knots and Mach, plus the pace equivalents runners and cyclists actually use.

Last reviewed: September 22, 2026Written and checked by the Life Calculator editorial team

The conversion factors

1 km/h = 0.27777… m/s (÷ 3.6) 1 mph = 0.44704 m/s exactly 1 knot = 1.852 km/h = 0.514444… m/s exactly 1 ft/s = 0.3048 m/s exactly Mach 1 ≈ 340.29 m/s at sea level, 15 °C

Metres per second is the SI unit and the sensible pivot for any conversion. The one useful thing to memorise: to get from km/h to m/s, divide by 3.6. To go back, multiply by 3.6.

For mph and km/h, multiply by 1.6 going one way and by 0.6 going the other. 60 mph is 96.6 km/h; 100 km/h is 62 mph.

Knots and Mach

A knot is one nautical mile per hour, and a nautical mile is one minute of latitude. That relationship is why ships and aircraft use it: a vessel making 10 knots covers 10 minutes of latitude in an hour, which can be read straight off a chart. The name comes from the chip log, a line knotted at fixed intervals and paid out behind a ship for a measured time.

Mach is a ratio rather than a fixed speed — the object's speed divided by the local speed of sound. Because the speed of sound depends on air temperature, Mach 1 is about 1,225 km/h at sea level but only around 1,062 km/h in the cold air at cruising altitude. An aircraft can therefore accelerate through Mach 1 by climbing without changing its actual speed.

Pace versus speed

Runners and swimmers think in pace — time per unit distance — while cyclists and drivers think in speed. They are reciprocals:

Pace (seconds per km) = 1000 ÷ speed in m/s Speed (km/h) = 3600 ÷ pace in seconds per km

The inversion matters because it makes pace behave counterintuitively: improving from 6:00/km to 5:30/km is a bigger gain in speed than improving from 4:00/km to 3:30/km, even though both are thirty seconds. Our running pace calculator handles splits and race predictions in detail.

Frequently asked questions

How fast is 100 km/h in mph?

62.14 mph. The reverse: 60 mph is 96.56 km/h, which is why speed limits of 60 mph and 100 km/h are treated as roughly equivalent.

Why do aircraft use knots rather than km/h?

Because navigation is done on charts marked in degrees and minutes of latitude, and one knot is exactly one minute of latitude per hour. It removes a conversion step from every calculation a navigator makes.

Is Mach 1 always the same speed?

No. It is the local speed of sound, which falls as air temperature falls. At sea level it is about 1,225 km/h; at 11,000 m in −56 °C air it is about 1,062 km/h. This calculator uses the sea-level standard value.