Convert Speed Units

Speed Converter

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Speed Conversion Chart

Key relationships between speed units. The SI unit is the meter per second (m/s).

SI & Metric

1 m/s=3.6 km/hexact
1 km/h≈0.27778 m/s(1/3.6, rounded)
1 km/s=3,600 km/hexact
1 cm/s=0.01 m/sexact

Imperial & US

1 mph=1.609344 km/hexact
1 mph=0.44704 m/sexact
1 ft/s=0.3048 m/sexact
1 ft/min=0.00508 m/sexact

Aviation & Reference

1 knot=1.852 km/hexact
1 knot=1.150779 mph
Mach 1=343 m/sat 20°C
Mach 1=1,235 km/hat 20°C

All metric↔imperial speed factors are exact, derived from the International Yard and Pound Agreement (1959): 1 mile = 1,609.344 m, 1 foot = 0.3048 m. The knot is defined as exactly 1 nautical mile per hour = 1,852 m/h. Mach number depends on temperature: Mach 1 ≈ 343 m/s at 20°C sea level, but varies with altitude and conditions.

About Speed Units

Road & Automotive

Speed limits and vehicle speedometers use km/h (most countries) or mph (US, UK, Myanmar). Quick mental shortcut: multiply km/h by 0.6 to estimate mph, or multiply mph by 1.6 to estimate km/h.

Aviation & Nautical

Airspeed and sea speed are measured in knots (nautical miles per hour). 1 knot = 1.852 km/h exactly. Aircraft also use Mach number for high-speed flight — Mach 1 is the speed of sound, which varies with altitude and temperature.

Science & Engineering

The meter per second (m/s) is the SI unit of speed. Used in physics, engineering, and weather reports (wind speed). Acceleration is measured in m/s², making m/s the natural unit for kinematic calculations.

Athletics & Running

Runners use pace (minutes per kilometer or per mile) rather than speed. A 5 min/km pace = 12 km/h = 7.46 mph. Sprint speeds: Usain Bolt's peak was 12.27 m/s ≈ 44.17 km/h.

Speed and velocity are often used interchangeably, but in physics they differ: speed is a scalar (magnitude only), while velocity is a vector (magnitude + direction). For unit conversion purposes, the distinction does not affect the calculation.

Road (km/h & mph)

Aviation & Nautical

Science & Engineering

Frequently Asked Questions

What is the difference between speed and velocity?

Speed is a scalar quantity that measures how fast an object moves, expressed as distance divided by time. Velocity is a vector quantity that includes both speed and direction. For example, 60 km/h is a speed, while 60 km/h north is a velocity. In everyday use, the terms are often interchangeable, but in physics they have distinct meanings.

Why do pilots and sailors use knots instead of km/h or mph?

Knots are tied to the nautical mile, which equals one minute of arc of latitude on Earth. This makes navigation calculations simpler when working with charts and coordinates. One knot equals approximately 1.852 km/h or 1.151 mph. All international aviation and maritime communications use knots as the standard speed unit.

What does Mach 1 mean and why does the speed of sound change with altitude?

Mach 1 equals the speed of sound in the surrounding air. At sea level and 15 degrees Celsius, that is about 1,225 km/h (761 mph). The speed of sound depends on air temperature, not pressure. At cruise altitude (35,000 ft), where temperature drops to about minus 57 degrees Celsius, the speed of sound decreases to roughly 1,062 km/h.

How do I convert between km/h and mph quickly?

For a quick estimate, multiply km/h by 0.6 to get mph, or multiply mph by 1.6 to get km/h. The exact factors are 0.621371 and 1.60934 respectively. For example, 100 km/h is about 62 mph, and 60 mph is about 97 km/h.

Related Calculators

Conversion factors verified against NIST, BIPM, ISO 80000-3 Derived from SI base units (m/s, BIPM). Last reviewed: March 2026
Adilson Fernandes By Adilson Fernandes
Tiago Fernandes Reviewed by Tiago Fernandes

All unit conversions on CoolConversion use conversion factors defined or documented by internationally recognised standards bodies (such as ISO and NIST), including both SI and non-SI units.