Speed Converter

Convert between meters per second, kilometers per hour, miles per hour, knots, feet per second, and Mach number.

Common Speed Conversions
FromToResult
100 km/hmph62.137 mph
60 mphkm/h96.561 km/h
1 m/skm/h3.6 km/h
1 Knotkm/h1.852 km/h
1 Machkm/h1,225 km/h
1 Machmph767.269 mph
30 mphm/s13.411 m/s
1 ft/skm/h1.09728 km/h

Frequently Asked Questions

Multiply km/h by 0.621371 to get mph. For a quick mental estimate, multiply by 0.6 (slightly under). For example, 100 km/h ≈ 62.1 mph. To convert mph to km/h, multiply by 1.60934.

A knot is 1 nautical mile per hour = 1.852 km/h = 1.15078 mph. It is used in aviation and maritime navigation. The term originated from sailors measuring speed by counting knots on a rope thrown overboard on a timed log line.

Mach number is the ratio of an object's speed to the speed of sound. At sea level and 20°C, Mach 1 ≈ 343 m/s ≈ 1,235 km/h ≈ 767 mph. It varies with altitude and temperature. Aircraft exceeding Mach 1 are supersonic; Mach 5+ is hypersonic.

The speed of light in vacuum is exactly 299,792,458 m/s (≈ 300,000 km/s = 670,616,629 mph). It is denoted as c and is a fundamental physical constant. Nothing with mass can reach or exceed this speed according to Einstein's theory of special relativity.

How It Works

Enter Speed

Enter any speed value. All units convert through meters per second as the SI base unit of velocity.

Select Units

Choose from metric, imperial, nautical, and Mach speed units. Swap direction with a single click.

Instant Result

Results are displayed instantly with the conversion factor. The reference table shows common speed equivalents.

Common Use Cases

Driving & Road Trips

Convert speed limits from km/h to mph or vice versa when driving in countries that use different speed measurement systems.

Aviation

Convert airspeed between knots, mph, and km/h for flight planning, reading aviation weather reports, and pilot training.

Weather & Wind

Convert wind speed measurements from knots or m/s (common in weather reports) to mph or km/h for easier interpretation.

Sports & Athletics

Convert running, cycling, and swimming speeds between m/s, km/h, and mph for international competition comparisons.

Maritime

Convert vessel speeds between knots and km/h for shipping route planning, fuel consumption estimates, and port logistics.

Physics & Engineering

Convert between m/s and other units for mechanics problems, fluid dynamics, and engineering calculations requiring SI units.

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