# Foot

A foot (ft or '), plural feet, is a unit of length in the U.S. customary and imperial systems of measurement. Since 1959, 1 foot has been defined as exactly 0.3048 meters (m). A meter is the base unit of length in the International System of Units (SI), the official system of measurement in most countries around the world.

While the United States uses SI in various areas such as science, medicine, industry, and the government, US customary units are still widely used throughout the country. To some degree, the UK and Canada still use the foot (and some other US customary units) even though both have officially adopted SI. Outside of these countries, US customary units are rarely used, with the exception of the international use of feet for measuring altitude in aviation.

Below are some of the relationships between the foot and other common units of length in both SI and the US customary system.

 1 foot =  12 inches 3 feet =  1 yard 1 foot =  0.3048 m = 30.48 cm = 304.8 mm 5280 feet =  1 mile

Being able to convert between feet and meters is important because meters are the standard unit of length used throughout most of the world. Standardization of units of measurement is important because it allows countries around the globe to effectively communicate with each other. If every country used different units of measurement, it would make communication less efficient, and errors would be more likely.

Example

Convert the following measurements between feet and meters.

1. 556 ft:

556 × 0.3048 = 169.469 m

2. 52 m:

52 × 3.28084 = 170.604

### Did you know?

The foot was originally derived from the use of the human body as a basis for units of length. There have been a number of other definitions since then, and the definition we use today is known as the international foot, which corresponds to a shoe size of 14 (US male), 15.5 (US female), 13(UK), or 48 (EU).

There are still other definitions of the foot used today such as the US survey foot. This is because there was already a lot of data in the US based on the definition of the foot prior to 1959, which varies slightly from its current definition. Rather than creating confusion between old and new survey data using different definitions of the foot, surveyors still use the survey foot in the US.