Cubic feet measure volume — the three-dimensional space a container or material occupies. Calculate it by multiplying length × width × height, with all measurements in feet. Cubic feet are used for storage units, shipping boxes, mulch, gravel, concrete, and appliance capacity.
The formula
cu ft = length (ft) × width (ft) × height (ft)
A space that is 10 ft long, 8 ft wide, and 6 ft tall: 10 × 8 × 6 = 480 cu ft.
Converting from inches to feet first
If your measurements are in inches, divide each by 12 before multiplying. Alternatively, multiply all three inch measurements and divide by 1,728 (since 12³ = 1,728).
Example: A moving box is 24 in × 18 in × 16 in.
24 × 18 × 16 = 6,912 cubic inches
6,912 ÷ 1,728 = 4 cubic feet
Practical examples
Example 1 — Storage unit
A 10 ft × 10 ft storage unit with an 8-foot ceiling is:
10 × 10 × 8 = 800 cu ft
A 5 ft × 10 ft unit is 400 cu ft. Standard refrigerators are 18–25 cu ft for reference.
Example 2 — Garden mulch
A flower bed is 20 ft long and 4 ft wide. You want to apply mulch 3 inches (0.25 ft) deep.
20 × 4 × 0.25 = 20 cu ft of mulch
Mulch is often sold in 2 cu ft bags: 20 ÷ 2 = 10 bags.
Example 3 — Concrete pour
A slab is 12 ft × 8 ft × 0.33 ft (4 inches thick).
12 × 8 × 0.33 = 31.7 cu ft = 1.17 cubic yards (divide by 27, since 3³ = 27)
Concrete is sold by the cubic yard in the US; always convert cubic feet ÷ 27 to get cubic yards before ordering.
Common cubic foot reference points
| Item | Approximate cubic feet |
|---|---|
| Standard refrigerator | 18–25 cu ft |
| Top-load washing machine | 3.5–5.5 cu ft |
| 5×5 storage unit | 200 cu ft |
| 5×10 storage unit | 400 cu ft |
| 10×10 storage unit | 800 cu ft |
| 20 ft moving truck | ≈1,000 cu ft |