Cubic feet measure volume. They are how US retailers rate refrigerators and freezers, how moving companies estimate truck space, how bagged mulch and potting soil are sold, and how shipping carriers work out dimensional weight. One cubic foot is a cube 12 inches on each side, which is 1,728 cubic inches. This cubic feet calculator gives the volume of a box or a cylinder from measurements in inches, feet, yards, centimetres or metres. It also converts the result to cubic yards, cubic metres, litres and US gallons, for one item or several identical ones.
For landscape materials sold by the cubic yard, the cubic yard calculator adds waste and cost. For soil in planters, the raised bed soil calculator counts bags.
How to use the cubic feet calculator
- Choose box or cylinder.
- Enter the inside dimensions if you want capacity, or the outside dimensions if you want the space an item takes up.
- Pick a unit for each measurement; you can mix them, such as a length in feet and a height in inches.
- Enter how many identical items to total.
Formula
A US liquid gallon is defined as exactly 231 cubic inches, so a cubic foot holds 1,728 ÷ 231 ≈ 7.48 gallons.
Worked example
A moving box measures 24 × 18 × 16 inches.
- Cubic inches: 24 × 18 × 16 = 6,912 in³.
- Cubic feet: 6,912 ÷ 1,728 = 4 ft³.
- Ten of these boxes: 40 ft³, or 1.48 yd³ (1.13 m³).
A cylindrical rain barrel 2 ft across and 3 ft tall holds π × 1² × 3 = 9.42 ft³, which is about 70.5 US gallons.
Volume conversion table
| 1 cubic foot equals | Value |
|---|---|
| Cubic inches | 1,728 |
| Cubic yards | 0.037037 (1/27) |
| Cubic metres | 0.028316846592 |
| Litres | 28.316846592 |
| US liquid gallons | 7.480519 |
| US dry quarts (bagged soil) | 25.714 |
Potting mix is often labelled in dry quarts: an 8 qt bag is about 0.31 ft³, and a 1.5 ft³ bag is about 38.6 dry quarts.
Inside vs outside dimensions
Appliance capacity is the usable inside volume, which is much smaller than the outer box. Wall thickness, insulation and shelves all take space. For moving and storage, measure the outside of the item and add a little for padding and awkward shapes. Shipping carriers calculate dimensional weight from outside dimensions in inches, divided by a carrier-specific divisor. Check your carrier's current divisor rather than assuming one.
For irregular shapes, split the object into boxes and cylinders, calculate each one and add them, or fill the container with water and measure the volume that way.
Caveats and assumptions
- Results assume straight sides; tapered pots, tubs and bags hold less than a box with the same top dimensions.
- Gallons are US liquid gallons (231 in³); an imperial gallon is larger, about 6.229 per cubic foot.
- Mixed units are converted to feet before multiplying.
- Values are rounded for display.
Frequently asked questions
How do I calculate cubic feet?
Multiply length × width × height with every measurement in feet. A 4 × 2 × 3 ft space is 24 ft³.
How do I convert cubic inches to cubic feet?
Divide by 1,728, because a cubic foot is 12 × 12 × 12 inches. 6,912 in³ ÷ 1,728 = 4 ft³.
How many gallons are in a cubic foot?
About 7.48 US liquid gallons, because a US gallon is exactly 231 cubic inches.
How many cubic feet are in a cubic yard?
27, because a yard is 3 feet and 3 × 3 × 3 = 27.
How do I find the cubic feet of a cylinder?
Multiply π by the radius squared by the height, all in feet. A tank 2 ft wide and 3 ft tall: 3.1416 × 1 × 3 = 9.42 ft³.
Sources
- NIST — SP 811 Appendix B.8, Factors for Units Listed Alphabetically — cubic foot, gallon and litre factors
- NIST Handbook 44 — Appendix C, General Tables of Units of Measurement — gallon = 231 cubic inches
- OpenStax Prealgebra 2e — 9.6 Solve Geometry Applications: Volume and Surface Area — volume of rectangular solids and cylinders
This calculator gives estimates for planning and education. Check measurements, local codes, supplier specs and your school's official policy before relying on a result. See our disclaimer and how we build and check calculators.