A cubic inch (in3) is a measure of the volume of a cube with edge lengths of 1 inch.
What is 1 cubic inch
1 cubic inch is equal to the volume of a cube with edges that measure 1 inch, as shown in the figure below.
How to find cubic inches
The volume of a cube is calculated as length × width × height. Since the cube in the figure above has edge lengths of 1 inch, its volume is 1 in3. The same formula can be used for 3D shapes that are not cubes. As long as the lengths of the edges are in inches, the result of multiplying length × width × height will be a volume in 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 for the volumes of other shapes. As long as their dimensions have units of inches, using their formulas will yield a volume in cubic inches.
Use of cubic inches
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.
Convert cubic inches
Below are the relationships between cubic inches and some commonly used units of volume in various systems of measurement.
Cubic inches to cubic feet
Cubic inches ÷ 1,728 = cubic feet
Cubic inches to cubic meters
Cubic inches ÷ 61,023.744 = cubic meters
Cubic inches to US gallons
Cubic inches ÷ 231 = US gallons
Cubic inches to liters
cubic inches ÷ 61.024 = liters
Cubic inches to milliliters
Cubic inches × 16.387 = milliliters
Since so many different units of volume are used, it is important to be able to convert between them.
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.