What is a cubic foot?
A cubic foot is the volume of a cube that measures one foot on every side. It is a standard way to measure the space inside things in the United States: moving boxes, refrigerators, freight, soil, concrete, bags of mulch and the storage capacity of a room or truck.
One cubic foot equals 1,728 cubic inches, about 7.48 US gallons, or about 28.3 liters. There are 27 cubic feet in a cubic yard.
How to calculate cubic feet of a box
- Measure the length, width and height.
- Convert all three to feet. Divide inches by 12.
- Multiply length × width × height.
If the measurements are already in different units, the calculator converts each one for you.
How to calculate cubic feet of a cylinder
A cylinder has a circle at the base, so find the area of the circle and multiply by the height. The radius is half the diameter.
- Convert the diameter and height to feet.
- Divide the diameter by 2 to get the radius.
- Square the radius and multiply by pi (3.14159).
- Multiply by the height.
Tips for accurate measurements
- Use inside measurements for capacity. To know how much a container holds, measure the inside, not the outside wall.
- Keep each unit straight. Mixing inches and feet in your head is the most common source of mistakes, so pick the right unit beside each number.
- Round up when buying. If you are ordering material, a little extra covers waste and settling.
- Irregular shapes: split them into simple boxes and cylinders, calculate each, then add the volumes. Use the quantity box for repeats.
Cubic feet conversion table
| Cubic feet | Cubic yards | US gallons | Liters |
|---|---|---|---|
| 1 | 0.037 | 7.48 | 28.3 |
| 5 | 0.185 | 37.4 | 141.6 |
| 10 | 0.370 | 74.8 | 283.2 |
| 27 | 1.000 | 202.0 | 764.6 |
| 100 | 3.704 | 748.1 | 2,831.7 |
Converting other volume units to cubic feet
- Cubic inches: divide by 1,728.
- Cubic yards: multiply by 27.
- Cubic meters: multiply by 35.3147.
- Liters: divide by 28.3168.
- US gallons: multiply by 0.13368 (or divide by 7.48).
A quick check for a typical number: a 55 gallon drum holds about 7.35 cubic feet. A standard 20 foot shipping container has an inside volume of roughly 1,170 cubic feet, though the exact figure depends on the model.
Cubic feet and appliances or storage
Refrigerators, freezers and storage units list their capacity in cubic feet, and it is measured on the inside. A 5 ft by 10 ft storage unit with an 8 ft ceiling holds 400 cubic feet, and a standard bedroom of 12 ft by 12 ft with an 8 ft ceiling has 1,152 cubic feet of air. Use the calculator to compare capacities quickly, and remember that you can rarely use 100 percent of a space because of gaps and shape.
Common uses
People use cubic feet to size a refrigerator or freezer, estimate shipping space, check how much soil a raised bed holds, work out the size of an air conditioner or heater for a room, and compare moving truck capacity. Always check whether a product is labeled in cubic feet, since bagged soil and mulch are often sold in 1, 2 or 3 cubic foot bags.
Why volume units matter
Volume numbers are easy to mix up because the same space can be expressed in many units. A pallet of goods may be quoted in cubic feet by the carrier, cubic meters by an overseas supplier, and liters or gallons by the product label. Converting everything to one unit before comparing avoids ordering too little or paying for too much space. This calculator shows the common conversions side by side so you can copy the one you need.