What is mile per hour?
Mile per hour is a unit of speed equal to one mile travelled in one hour. It is the standard unit for road speeds, vehicle performance ratings, and weather reports in the United States and United Kingdom.
Real-world uses
Miles per hour is the standard speed unit for road traffic in the United States, the United Kingdom, and a few other countries. Baseball pitching speed, hurricane wind categories (Saffir-Simpson scale), and NASCAR race speeds are quoted in mph.
History
Miles per hour became the standard speed expression in English-speaking countries with the advent of railways and later automobiles. The first US speed limit (8 mph in New York City, 1901) and British speed cameras use mph as the legal standard.
Common mistakes
Assuming mph-to-km/h conversion is a simple ×1.5—the actual factor is 1.609. Also, forgetting that UK and US speed limits both use mph, which can mislead visitors from metric countries into driving too fast or too slow.
What is kilometre per hour?
Kilometre per hour is a unit of speed equal to one kilometre travelled in one hour. It is the most widely used unit for road speed limits, vehicle speedometers, and wind speeds in metric countries.
Real-world uses
Kilometres per hour is the standard speed unit for road traffic in most countries, displayed on car speedometers, speed limit signs, and GPS devices. Weather services report wind speeds in km/h, and athletes track running pace in min/km.
History
Kilometres per hour became widespread as the metric system was adopted for road transport in the 20th century. The first metric speed limits appeared in continental Europe. Today, km/h is used in about 91% of the world's countries for traffic regulation.
Common mistakes
Confusing km/h with m/s—100 km/h is about 27.78 m/s, not 100 m/s. Also, when converting to mph, people often use a rough factor of 1.5 instead of the correct 1.609, leading to inaccurate speed comparisons.
When is this conversion used?
Converting between mile per hour and kilometre per hour is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region. Speed limits, vehicle speedometers, and weather reports for wind speeds use different units depending on the country, making km/h to mph conversion one of the most practical speed conversions.
Worked examples
1 mile per hour = 1.609344 kilometre per hour
1 kilometre per hour = 0.27777778 metre per second
How to convert mile per hour to kilometre per hour
To convert mile per hour to kilometre per hour, multiply the value by 1.609344.
To convert kilometre per hour back to mile per hour, multiply by 0.62137119.
Measurement standards
The SI unit of speed is metres per second (m/s), a derived unit requiring no independent definition. The knot is defined as exactly one nautical mile (1,852 metres) per hour and is sanctioned for maritime and aeronautical navigation by the International Civil Aviation Organization.
Did you know?
The fastest human-made object is the Parker Solar Probe, which reached 635,266 km/h (about 176 km/s) in 2024 during a close pass of the Sun — fast enough to travel from New York to Tokyo in under a minute.
Quick reference: mile per hour to kilometre per hour
| mile per hour | kilometre per hour |
|---|---|
| 0.1 | 0.1609344 |
| 0.5 | 0.804672 |
| 1 | 1.609344 |
| 2 | 3.218688 |
| 5 | 8.04672 |
| 10 | 16.09344 |
| 25 | 40.2336 |
| 50 | 80.46719999 |
| 100 | 160.93439999 |
| 250 | 402.33599997 |
| 500 | 804.67199994 |
| 1,000 | 1,609.34399987 |
Common values
| mile per hour | kilometre per hour | |
|---|---|---|
| Walking speed | 3.13171081 mile per hour | 5.04 kilometre per hour |
| City speed limit | 31.09341446 mile per hour | 50.04 kilometre per hour |
| Highway driving | 70.01610594 mile per hour | 112.67999999 kilometre per hour |
| Commercial aircraft | 559.23407301 mile per hour | 899.99999993 kilometre per hour |
| Speed of sound (sea level) | 761.20705082 mile per hour | 1,225.0439999 kilometre per hour |
Available Speed units
More mile per hour conversions
- Convert mile per hour to metre per second
- Convert mile per hour to kilometre per hour
- Convert mile per hour to knot
- Convert mile per hour to foot per second
- Convert mile per hour to metre per minute
- Convert mile per hour to kilometre per second
- Convert mile per hour to mach (approx at sea level)
- Convert mile per hour to centimetre per second
- Convert mile per hour to mile per minute
Assumption: Mach uses an approximate sea-level reference (about 340.29 m/s).