# Cubic inches

A cubic inch (in3) is a measurement of volume in the US customary and imperial systems of measurement. 1 cubic inch is equal to the volume of a cube with edges that measure 1 inch each.

Since the volume of a cube is calculated as length × width × height, the volume of the cube is 1 in3. The above cube can be referred to as a unit cube, where the unit in this case is the inch. 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 in3, the volume of the object is 16 in3.

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 inch 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). Even in the US, cubic inches are not widely used. The automotive industry is one of the few areas in which cubic inches are still used, mostly for measuring engine displacement, or more specifically, cubic inch displacement. However, liters are also used for this same purpose, particularly when referencing newer cars, and cubic inch displacement is mostly used in the context of classic car collecting.

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 inches and some commonly used units of volume in various systems of measurement.

• 1,728 cubic inches = 1 cubic foot
• 61,023.744 cubic inches = 1 cubic meter
• 231 cubic inches = 1 US gallon
• 61.024 cubic inches = 1 liter
• 1 cubic inch = 16.387 milliliters

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

Example

The Cadillac Series 353 had a 353 cubic inch engine. What is its engine displacement in liters (L)?

There are 61.024 in3 in 1 L, so dividing 353 by 61.024 will yield the engine displacement in in3.

353 ÷ 61.024 = 5.785 L

A 353 in3 has an engine displacement of 5.785 L. Typically, this value is rounded up, and the engine displacement would be reported as 5.8 L.