Speed Converter

Speed / Velocity Converter

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Full Reference Table

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UnitValue

Speed Unit Conversion Guide

Speed is measured in many different units depending on the context — road travel, aviation, maritime navigation, and physics all use different standards. Our free online speed converter handles the six most important speed units, with instant results and a full reference table for any value you enter.

Kilometers per Hour (km/h)

Kilometers per hour is the standard unit for road speed in most countries. Speed limit signs, car speedometers, and weather reports use km/h in Europe, Asia, Africa, and Australia. One km/h equals approximately 0.621 mph or 0.2778 m/s.

Miles per Hour (mph)

Miles per hour is the standard road speed unit in the United States and the United Kingdom. One mph equals 1.60934 km/h. US and UK speed limits are posted in mph, and many American vehicles only display mph on their speedometers.

Meters per Second (m/s)

The SI unit of speed is meters per second. It is used in physics, engineering, and scientific contexts. One m/s equals 3.6 km/h or 2.237 mph. The speed of sound (approximately 343 m/s) and the speed of light (299,792,458 m/s) are expressed in m/s.

Knots (nautical miles per hour)

One knot equals one nautical mile per hour, or 1.852 km/h. Knots are the standard unit for speed in aviation and maritime navigation worldwide. Aircraft cruising speeds are given in knots (e.g., a commercial airliner cruises at about 450–500 knots).

Mach Number

Mach is the ratio of an object's speed to the speed of sound in the surrounding medium. At sea level in dry air at 20°C, Mach 1 ≈ 1,234.8 km/h (767 mph). Mach 2 is twice the speed of sound. Supersonic aircraft and missiles use Mach as their speed reference.

Frequently Asked Questions

How do I convert km/h to mph?
Multiply the km/h value by 0.621371. For example, 100 km/h × 0.621371 = 62.14 mph. Equivalently, you can divide by 1.609344. This conversion is essential for drivers crossing between metric and imperial countries.
How fast is Mach 1 in km/h?
Mach 1 at sea level in standard conditions (20°C, dry air) is approximately 1,234.8 km/h (767 mph or 343 m/s). The exact value varies with altitude, temperature, and air density, which is why Mach is a ratio rather than a fixed unit.
What is a knot in km/h?
One knot equals exactly 1.852 km/h. A ship travelling at 20 knots is moving at 37.04 km/h. Aircraft speeds at cruise altitude are typically reported in knots — a commercial jet at 480 knots equals about 889 km/h.
What is the speed of light in km/h?
The speed of light in a vacuum is 299,792,458 m/s, which equals approximately 1,079,252,849 km/h (about 1.08 billion km/h). In mph, this is about 670,616,629 mph. Nothing with mass can reach or exceed this speed.
How many feet per second is 60 mph?
60 mph equals exactly 88 feet per second (ft/s). This is a well-known engineering reference: 1 mph = 1.466667 ft/s, and 60 × 1.466667 = 88 ft/s. It is useful for calculating stopping distances and reaction times.