How to Calculate Cubic Feet: Box, Cylinder, Sphere and Conversions
The volume of a box is length × width × height, in feet, which gives cubic feet. A box 10 × 8 × 6 ft is 480 cubic feet, which is 17.78 cubic yards or 3,591 US gallons. The cubic feet calculator also does cylinders and spheres.
The formulas
| Shape | Formula | Example | Cubic feet |
|---|---|---|---|
| Box | length × width × height | 10 × 8 × 6 ft | 480 |
| Cylinder | π × radius² × height | 4 ft across, 6 ft high | 75.4 |
| Sphere | 4/3 × π × radius³ | 4 ft across | 33.5 |
Converting cubic feet
What one cubic foot is in other units:
| Unit | Symbol | In one cubic foot |
|---|---|---|
| Cubic feet | ft³ | 1.00 |
| Cubic yards | yd³ | 0.0370 |
| US gallons | gal | 7.48 |
| Liters | L | 28.32 |
| Cubic meters | m³ | 0.0283 |
| Cubic inches | in³ | 1,728 |
Volumes of some common boxes
| Box | Cubic feet | Cubic yards | US gallons |
|---|---|---|---|
| 2 × 2 × 2 ft | 8.0 | 0.30 | 60 |
| 4 × 4 × 4 ft | 64.0 | 2.37 | 479 |
| 10 × 8 × 6 ft | 480.0 | 17.78 | 3,591 |
| 12 × 12 × 4 ft | 576.0 | 21.33 | 4,309 |
| 20 × 10 × 0.5 ft | 100.0 | 3.70 | 748 |
Tips
- Measure in feet, or convert inches to feet first: divide by 12. Mixed units are the commonest cause of wrong answers.
- Divide cubic feet by 27 for cubic yards, the unit soil, gravel and concrete are sold in.
- For an irregular space, split it into boxes and cylinders, and add up the volumes.
- Measure the inside of a container, and the outside of a space you will fill.
- A cubic foot of water weighs 62.4 pounds, so a full tank can be heavier than it looks.
For soil, mulch, gravel and concrete, use the cubic yard calculator or the calculator for the material, which allow for waste. For tanks, see the tank volume calculator.
Frequently asked questions
How do you calculate cubic feet?
Multiply length by width by height, all in feet. A box 10 × 8 × 6 ft is 480 cubic feet.
How many cubic feet are in a cubic yard?
27, because a yard is 3 ft and 3 × 3 × 3 = 27.
How many gallons are in a cubic foot?
About 7.48 US gallons. The 10 × 8 × 6 ft box holds 3,591 gallons.
How do you find the cubic feet of a cylinder?
π × radius² × height. A cylinder 4 ft across and 6 ft high is 75.4 cubic feet.
How do you find the volume of a sphere?
4/3 × π × radius³. A sphere 4 ft across is 33.5 cubic feet.
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