Converting Inches to Cubic Feet

The cubic foot is a non-metric unit for measuring volume. The definition of a cubic foot is the volume of a cube with sides that measure 1 linear foot. As you make the mathematical conversion, remember that 1 cubic foot equals 1,728 cubic inches.

The Formula

Step 1

Multiply the length times the width times the height (sometimes referred to as depth) of any three-dimensional figure. Picture a cube in your mind. This cube measures 1 linear foot in length, 1 linear foot in width and 1 linear foot in height.

Step 2

Convert the feet to linear inches. A single linear foot converts to 12 linear inches. The cube in your mind’s picture measures 12 inches wide, 12 inches long and 12 inches deep.

Step 3

Calculate the volume of your cube in cubic inches by multiplying the length x the width x the depth. Therefore, 12 inches x 12 inches x 12 inches equals 1,728 cubic inches (or 1,728 inches cubed).

Step 4

Express your equation: 12³ = 1,728, or 12 x 12 x 12 = 1,728 cubic inches.

Step 5

Divide the result by the number of cubic inches in a cubic foot (1,728) if you need to find the total in cubic feet. In this example, since you started with a cube with 1 foot sides, 1,728 / 1,728 = 1 cubic foot.

Test-drive the Formula

Step 1

Give your cube some dimensions so that you can try this out. Use this example: the three sides of the cube measure 100 linear inches, 30 linear inches and 40 linear inches. To get the figure for total linear inches, multiply 100 x 30 x 40. Your total comes to 120,000 cubic inches.

Step 2

Divide the result in cubic inches (120,000) by the number of cubic inches in a cubic foot (1,728). This is expressed like this: 120,000 / 1,728 = 69.44444 cubic feet.

Step 3

Round that final number down to two decimal places if you want, so your final calculation for the number of cubic feet in your cube is 69.44.

Warning

Double-check your calculations even if you are using a calculator.