Foot (Unit of Measurement) — Definition, Formula & Examples

A foot is a unit of length in the U.S. customary system equal to 12 inches. The plural of foot is feet, and it is abbreviated as "ft."

One foot is defined as exactly 0.3048 meters (or 30.48 centimeters). In the U.S. customary and imperial systems, 1 foot equals 12 inches and 3 feet equal 1 yard.

Key Formula

1 \text{ ft} = 12 \text{ in}

Where:

$\text{ft}$ = feet, the larger unit
$\text{in}$ = inches, the smaller unit (12 per foot)

How It Works

You use feet to measure medium-sized lengths like your height, the length of a room, or the height of a basketball hoop. To convert feet to inches, multiply by 12. To convert inches to feet, divide by 12. When a measurement includes both feet and inches, you write it like

5 \text{ ft } 4 \text{ in}

, which means 5 feet and 4 inches.

Worked Example

Problem: A bookshelf is 48 inches tall. How many feet tall is it?

Set up the conversion: Since 1 foot equals 12 inches, divide the total inches by 12.

48 \div 12

Calculate: 48 divided by 12 equals 4.

48 \div 12 = 4

Answer: The bookshelf is 4 feet tall.

Why It Matters

Feet appear constantly in everyday life — road signs, building plans, and sports fields all use feet. Being comfortable converting between feet and inches helps you solve word problems in math class and read real-world measurements accurately.

Common Mistakes

Mistake: Confusing feet and yards when converting. Some students multiply by 3 when they should multiply by 12 (or vice versa).

Correction: Remember: 1 foot = 12 inches, and 1 yard = 3 feet. To go from feet to inches, multiply by 12. To go from yards to feet, multiply by 3.