Inches, Feet, Miles and Meters: Where Length Units Come From and Who Uses Them
Almost every country measures length in meters, yet inches, feet and miles are still everywhere: on American road signs, British pub chalkboards, TV boxes worldwide and airline cockpits. Here’s where each unit came from and who still uses it.
Need a quick answer? Use the length converter.
Who uses what today
| Country or context | Everyday length units |
|---|---|
| Most of the world | Meters, centimeters, kilometers |
| United States | Inches, feet, yards and miles for almost everything outside science, medicine and the military |
| United Kingdom | Metric for most things, but road distances and speed limits are in miles, and people often give their height in feet and inches |
| Canada | Metric officially (road signs are in kilometers), but height in feet and inches and building lumber in inches are still common |
| Aviation (nearly worldwide) | Altitude in feet, distance in nautical miles |
| Shipping (worldwide) | Nautical miles, and speed in knots (nautical miles per hour) |
| Screens, tires, pipes | Inches, almost everywhere |
The US, Liberia and Myanmar are often cited as the only countries that haven’t fully adopted the metric system. Liberia and Myanmar have both announced plans to go metric, which leaves the US as the main holdout in everyday life. Even there, the customary units are officially defined in terms of metric ones.
The meter
The meter is a product of the French Revolution. In 1791 the French Academy of Sciences proposed a new unit based on nature rather than on any king’s body: one ten-millionth of the distance from the North Pole to the equator, measured along the meridian through Paris. Two astronomers, Jean-Baptiste Delambre and Pierre Méchain, spent most of the 1790s surveying the arc between Dunkirk and Barcelona to pin it down, and a platinum bar representing the result was made in 1799.
The name comes from the Greek metron, “measure”. In 1875, seventeen nations signed the Metre Convention, creating an international bureau to look after the units. The meter has been redefined as measurement has improved: first by a platinum-iridium bar (1889), then by the wavelength of light from krypton-86 (1960), and since 1983 as the distance light travels in a vacuum in 1/299,792,458 of a second.
The inch
“Inch” comes from the Latin uncia, meaning “one twelfth”: an inch is a twelfth of a foot. (The same word gave us “ounce”, a twelfth of a Roman pound.) A medieval English definition set the inch as the length of three grains of barley, dry and round, laid end to end.
Over the centuries the inch drifted slightly between countries. In 1959, the US, UK, Canada, Australia, New Zealand and South Africa agreed to define it as exactly 2.54 centimeters, which is why the conversion is a neat number.
The foot
The foot is about as old as measurement itself, and was, roughly, the length of a human foot. The Romans used a pes of about 29.6 cm, divided into twelve unciae. Many European towns had their own foot until the metric system replaced them. The English foot of 12 inches is now exactly 0.3048 meters.
The yard
The origin of the yard is murky. A popular story says King Henry I of England defined it as the distance from his nose to the tip of his outstretched thumb, but that’s more legend than record. The yard became the standard English unit of length, kept as a physical bar in London for centuries. Today it’s 3 feet, exactly 0.9144 meters, and you’ll still see it in American football and on golf courses.
The mile
The word “mile” comes from the Roman mille passus: a thousand paces, where a pace was two steps (left and right), about 1.48 km in total. The English mile wandered for centuries until a 1593 act of Parliament under Elizabeth I fixed it at 8 furlongs, or 5,280 feet. A furlong (“furrow long”) was the length of a plowed field, which is why the statute mile is such an odd number of feet.
A mile is exactly 1,609.344 meters.
The nautical mile
Sailors needed a unit that matched their maps. A nautical mile was originally one minute of latitude, a sixtieth of a degree, so distances could be read straight off a chart. Because Earth isn’t a perfect sphere, that distance varies slightly, so in 1929 an international conference fixed it at exactly 1,852 meters. The US adopted that value in 1954 and the UK in 1970.
Ships and aircraft everywhere still use nautical miles, and a knot is one nautical mile per hour.
Quick reference
- 1 inch = 2.54 cm (exact)
- 1 foot = 12 inches = 30.48 cm
- 1 yard = 3 feet = 0.9144 m
- 1 mile = 5,280 feet = 1.609344 km
- 1 nautical mile = 1,852 m ≈ 1.15 miles
Convert any of these with the length converter.