Cubic Feet Calculator
Bagged soil, mulch, gravel and sand are sold in cubic feet, and so are planters, raised beds and storage bins. Enter the three dimensions in any unit — inches, feet, yards, centimeters or meters — for a box, or the diameter and height for a round planter or tube, and the calculator returns cubic feet, cubic inches, cubic yards, gallons, liters and the number of bags to fill it. Conversions use the exact NIST Handbook 44 values.
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Worked example: 8 × 4 ft raised bed, 1 ft deep
| Step | Working | Result |
|---|---|---|
| Cubic feet | 8 × 4 × 1 | 32 cu ft |
| Cubic yards | 32 ÷ 27 | 1.19 yd³ |
| Gallons | 32 × 7.4805 | 239.4 gal |
| 2 cu ft bags | 32 ÷ 2 | 16 bags |
Measured in inches? Divide by 1,728
| Container | Working | Cubic feet |
|---|---|---|
| 24 × 18 × 12 in planter | 5,184 ÷ 1,728 | 3 cu ft |
| 36 × 12 × 10 in window box | 4,320 ÷ 1,728 | 2.5 cu ft |
| Round pot, 24 in across, 18 in deep | 3.1416 × 12² × 18 ÷ 1,728 | 4.71 cu ft |
Conversions are the exact NIST Handbook 44 values: 1 cubic foot = 1,728 cubic inches = 28.317 liters = 7.4805 U.S. gallons, and 27 cubic feet make a cubic yard. Bags of soil, mulch and gravel list their volume in cubic feet on the front, so divide the cubic feet you need by that number and round up.
Filling a raised bed? The raised bed soil calculator sizes the mix, and the bagged gravel calculator compares bags with bulk. For anything sold by the yard, use the cubic yard calculator.
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Frequently asked questions
- How do I calculate cubic feet?
- Multiply length × width × height with all three in feet. An 8 × 4 ft raised bed 1 ft deep is 8 × 4 × 1 = 32 cubic feet. If you measured in inches, multiply the three numbers and divide by 1,728.
- How many cubic feet are in a cubic yard?
- 27 cubic feet (3 ft × 3 ft × 3 ft). So 32 cubic feet is 32 ÷ 27 = 1.19 cubic yards.
- How do I convert inches to cubic feet?
- Multiply the three dimensions in inches and divide by 1,728, the number of cubic inches in a cubic foot. A 24 × 18 × 12 in planter holds 5,184 ÷ 1,728 = 3 cubic feet.
- How many gallons are in a cubic foot?
- 7.48 U.S. gallons (NIST: 7.480 519). A 4 × 2 × 1 ft box holds 8 cu ft, or about 59.8 gallons; 1 cu ft is also 28.3 liters.
- How many bags of soil do I need for 32 cubic feet?
- 16 bags of 2 cu ft, 11 bags of 3 cu ft or 32 bags of 1 cu ft. Divide the cubic feet by the bag size printed on the bag and round up.
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