How to Calculate Cubic Feet in a Room

Measure a square or rectangular room along the floor from one wall to the one directly across from it to get the width of the room. Write the width down in inches. For example, a room that is 9 feet 5 inches wide would be written as 113 inches. Use decimals for portions of an inch, such as 113.5 for 113 ½ inches.

Measure the length of the room in the opposite direction, along the floor from wall to wall. Write the length down in inches as well.

Measure the room from the ceiling to the floor to get the height of the room. Write that measurement down in inches.

Multiply the width by the length by the height. For example, if your room is 113 inches wide, 168 inches long and 99 inches high, multiply 113 by 168 for a product of 18,984. Then multiply 18,984 by 99 for a product of 1,879,416 inches as a result.

Divide the result by 144 to find out the cubic inches of the room. There are 144 cubic inches in a cubic foot, so in our example we would plug the numbers 1,879,416 and divide by 144, for an answer of 13,051.5.

Divide that answer by 12 get your cubic foot measurement. In our example, we would divide 12,051.5 by 12, for a total of 1,087.625 cubic feet, or a little over 1,087 ½ feet.

Get a rougher estimate, if you prefer, by just using feet to calculate. For example, 9.5 feet multiplied by 14 feet multiplied by 8.25 feet gives you a room volume of 1,097 1/4 feet, only about 10 feet off the calculation by inches. It’s not as precise, but it is close enough to work with as a rough estimate