How to calculate cubic feet
Multiply length × width × height, with every measurement in feet. If you measured in inches, multiply the three inch measurements and divide by 1,728, because a cubic foot is 12 × 12 × 12 = 1,728 cubic inches.[1]
cubic feet = length (ft) × width (ft) × height (ft) = inches³ ÷ 1,728
For mixed units, convert inches to feet first: 6 in = 0.5 ft, 9 in = 0.75 ft. A 10 ft × 6 ft area 9 inches deep is 10 × 6 × 0.75 = 45 cubic feet.
Cubic feet of a cylinder
A cylinder holds 3.1416 × diameter² ÷ 4 × height. A round tank 2 ft across and 4 ft tall holds 3.1416 × 4 ÷ 4 × 4 = 12.57 cubic feet, or about 94 US gallons.[1]
Worked examples
| Item | Cubic feet | Cubic yards | Liters | US gallons |
|---|---|---|---|---|
| Moving box 18 × 18 × 16 in | 3 | 0.111 | 85 | 22 |
| Raised bed 4 × 8 ft, 1 ft deep | 32 | 1.185 | 906 | 239 |
| Room 12 × 10 ft, 8 ft ceiling | 960 | 35.556 | 27,184 | 7,181 |
| Round planter 3 ft across, 2 ft deep | 14.14 | 0.524 | 400 | 106 |
| Tank 2 ft across, 4 ft tall | 12.57 | 0.465 | 356 | 94 |
Cubic feet to other units
One cubic foot is 28.3168 liters, 7.4805 US gallons and 1/27 of a cubic yard, from the exact definition of the foot (0.3048 m).[1]
| From 1 cubic foot to | Value |
|---|---|
| Cubic inches | 1,728 |
| Cubic yards | 0.037037 |
| Liters | 28.3168 |
| Cubic meters | 0.0283168 |
| US gallons | 7.4805 |
To convert a volume you already have, use cubic feet to cubic yards; for landscape materials spread to a depth, the cubic yard calculator and square feet to cubic yard calculator work from area and depth.
Inside or outside?For boxes and containers, measure the inside to find what fits, and the outside to find the space the box takes up.
Common mistakes
The most common mistake is mixing feet and inches: 10 ft × 6 ft × 9 in is not 540, it is 45 cubic feet.
- Dividing inches by 12 once. Cubic inches need ÷ 1,728 (12 × 12 × 12), not ÷ 12.
- Using the radius as the diameter. The cylinder formula above uses the full diameter.
- Converting to yards with 9. Nine converts square feet to square yards; cubic feet need 27.
Frequently asked questions
How do I calculate cubic feet?
Multiply length × width × height in feet. For inches, multiply them and divide by 1,728.
How many cubic feet are in a cubic yard?
27 cubic feet.[1]
How many gallons are in a cubic foot?
About 7.48 US gallons.[1]
How many cubic feet is a 12 × 12 × 12 inch box?
Exactly 1 cubic foot: 1,728 cubic inches ÷ 1,728.