How to Calculate Cubic Feet
Part of Area & Volume
Quick answer
Multiply length × width × height with all three in feet: cubic feet = L × W × H. If your measurements are in inches, multiply them together and divide by 1,728 (that's 12³). A box 3 ft on every side is 3 × 3 × 3 = 27 cubic feet — one cubic yard.
Cubic feet measure volume — the space inside a box. You get it by multiplying the three dimensions together, as long as they're all in the same unit. The only trick is converting inches to feet first.
The formula
Cubic feet = Length (ft) × Width (ft) × Height (ft)
From inches: multiply length × width × height in inches, then divide by 1,728. For depth that's in inches (a 4-inch slab, say), just convert it to feet first — 4 ÷ 12 = 0.33 ft.
Convert cubic feet to other units
| Cubic feet | Cubic yards (÷27) | US gallons (×7.48) |
|---|---|---|
| 1 ft³ | 0.037 yd³ | 7.5 gal |
| 10 ft³ | 0.37 yd³ | 74.8 gal |
| 27 ft³ | 1 yd³ | 202 gal |
| 100 ft³ | 3.70 yd³ | 748 gal |
Cubic feet of common containers
| Container | Approx. cubic feet |
|---|---|
| 5-gallon bucket | 0.67 ft³ |
| 1.5 cu ft bag of soil | 1.5 ft³ |
| 2 cu ft bag of mulch | 2 ft³ |
| Contractor wheelbarrow | 6 ft³ |
For bulk materials like concrete, soil, gravel or mulch, find the cubic feet, then divide by 27 to order in cubic yards. The cubic feet calculator shows yards, gallons and cubic meters at once.
FAQs
How many cubic feet are in a bag of soil?
Whatever the bag says — soil and mulch are sold by volume, with the cubic feet printed on the bag. Common sizes are 0.75, 1, 1.5 and 2 cubic feet. A 1.5 cu ft bag holds exactly 1.5 ft³.
How many cubic feet are in a 5-gallon bucket?
About 0.67 cubic feet. There are 7.48 gallons in a cubic foot, so 5 ÷ 7.48 = 0.668 ft³. A standard 5-gallon bucket is the everyday benchmark for two-thirds of a cubic foot.
How do I calculate cubic feet from inches?
Multiply length × width × height in inches, then divide by 1,728 (because 12 × 12 × 12 = 1,728). For example, 24 × 24 × 24 in = 13,824 ÷ 1,728 = 8 cubic feet.