Cubic feet

A cubic foot (ft3) is a measurement of volume in the US customary and imperial systems of measurement. 1 cubic foot is equal to the volume of a cube with edges that measure 1 foot each.

Since the volume of a cube is calculated as length × width × height, the volume of the cube is 1 ft3. The above cube can be referred to as a unit cube, where the unit in this case is the foot. One way to visualize volume is through use of unit cubes. For example, there are 16 unit cubes in the figure below. Since each cube measures 1 ft3, the volume of the object is 16 ft3.

In this manner, the volume of an object can be estimated as the number of unit cubes that fit within the object. In the above example, since the rectangular prism can be broken down into whole numbers of unit cubes, its volume can be calculated exactly. In cases where this is not possible, volume can be estimated using a combination of whole and partial unit cubes. Also, there are numerous formulas (such as length × width × height) that can be used to measure the volumes of various shapes.

Units of volume

A cubic foot is just one of many different units of volume. It is primarily used in the United States. Although it is also used to some degree in Canada and the UK, it is not common, since both Canada and the UK have adopted the International System of Units (SI). The volume of a refrigerator, the amount of water a household uses, and the size of a storage unit are a few examples of things that are measured using cubic feet.

Most of the rest of the world uses SI units of volume. The SI base unit of volume is the cubic meter, but the liter, an SI derived unit of volume, is also commonly used. There are many other measurements of volume in various systems of measurement, but most countries use either SI, the US customary (or imperial) system, or some combination of the two. Below are the relationships between cubic feet and some commonly used units of volume in various systems of measurement.

• 1 cubic foot = 1,728 cubic inches
• 1 cubic foot = 28.3168 liters
• 1 cubic foot = 7.4805 US gallons
• 35.315 cubic feet = 1 cubic meter

Since so many different units of volume are used, it is important to be able to convert between them.

Example

An Olympic-size pool contains approximately 2,500,000 liters (L) of water. How many cubic feet of water does the pool contain?

There are 28.3168 L in 1 ft3, so dividing 2,500,000 by 28.3168 will yield the volume in ft3.

2,500,000 ÷ 28.3168 = 88,286.812 ft3