Foot (unit) facts for kids

The foot is a unit used to measure length. It is part of the Imperial and U.S. customary systems. You often see it written as "ft" or with a special symbol called a prime ( ′ ).

One foot is made up of 12 inches. This is the same as 30.48 centimetres. It's called a "foot" because it was originally based on the length of a human foot!

History of the Foot

For a long time, the foot was a common way to measure things across Europe. But here's the tricky part: its length often changed! It wasn't just different from country to country, but even from city to city.

Because people's feet are all different sizes, measurements weren't always the same. This meant you couldn't always trust a measurement from one person to another. To fix this, King Henry I of England made a rule. He said the foot should be as long as his own foot. This was one of the first times a standard measurement was put into place.

Later, in 1959, several countries decided to make things even more consistent. The United States, Canada, New Zealand, South Africa, Australia, and the United Kingdom signed an agreement. It was called the 'International Yard and Pound Agreement'. This agreement made sure that the length of the foot (and other measurements) was the same in all these countries. These standard lengths are still used today in the Imperial and U.S. customary systems.

How the Foot is Used

You'll often see the foot used in everyday life, especially in the U.S. and the UK.

Measuring Height

In the U.S. and the UK, people usually measure a person's height using feet and inches. For example, if someone is "five foot eleven," it means they are 5 feet and 11 inches tall. This is about 180 centimeters. You might see this written as 5′ 11″.

Road Signs and Altitude

Road signs that show how tall a vehicle can be (height restrictions) often use feet and inches in the United States and the United Kingdom. You might also find that altitude (how high something is above sea level) is sometimes given in feet, even in countries that mostly use the metric system.

Foot Length in Centimeters

One foot is exactly 30.48 centimetres long. This is the official length agreed upon by countries around the world.

Images for kids

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  This old picture shows how people used to measure a "rod" and "feet." They would line up the left feet of 16 random people coming from church!

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  These are old measurement standards you can see at the Royal Observatory in Greenwich. They show the official lengths for imperial units.

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  This page from an 1848 Austrian math textbook shows different foot measurements from that time.

See also

In Spanish: Pie (unidad) para niños