cube volume calculator
A cube volume calculator cubes the side length (V = s × s × s): a 3 ft cube holds 27 cu ft, exactly 1 cubic yard, or about 202 gallons (764.6 liters).
How do you find the volume of a cube?
A cube volume calculator multiplies the side length by itself three times. Measure one edge in feet, then work out side × side × side to get cubic feet. Divide by 27 for cubic yards, or multiply by 7.48 for US gallons. A cube 3 ft on each side holds 27 cubic feet, which is exactly 1 cubic yard, or 202 gallons.
Enter the side length in feet. The calculator returns cubic feet, cubic yards, gallons, and liters.
The formula in plain words
- Cubic feet = side × side × side
- Cubic yards = cubic feet ÷ 27
- Gallons = cubic feet × 7.48052
- Liters = gallons × 3.78541
The 27 comes from a cubic yard being a 3 ft cube: 3 × 3 × 3 = 27 cubic feet. A 3 ft cube is a handy picture of a “yard” of mulch, gravel, or concrete.
Worked examples
These results match the calculator.
- A 3 ft cube (one cubic yard)**
- Cubic feet: 3 × 3 × 3 = 27.00 ft³
- Cubic yards: 27 ÷ 27 = 1.000 yd³
- Gallons: 27 × 7.48052 = 202.0 gal
- Liters: 764.6 L
- A 4 ft cube water tank**
- Cubic feet: 4 × 4 × 4 = 64.00 ft³
- Cubic yards: 64 ÷ 27 = 2.370 yd³
- Gallons: 64 × 7.48052 = 478.8 gal
- Liters: 1,812.3 L
Water weighs about 8.34 lb per gallon, so that full tank holds roughly 3,990 lb of water. Spread over a 16 sq ft base, that is about 250 lb per square foot on whatever it sits on.
Cube volume table
| Side | Cubic feet | Cubic yards | Gallons | Liters |
|---|---|---|---|---|
| 6 in (0.5 ft) | 0.125 | 0.005 | 0.9 | 3.5 |
| 1 ft | 1.00 | 0.037 | 7.5 | 28.3 |
| 1.5 ft | 3.38 | 0.125 | 25.2 | 95.6 |
| 2 ft | 8.00 | 0.296 | 59.8 | 226.5 |
| 2.5 ft | 15.63 | 0.579 | 116.9 | 442.5 |
| 3 ft | 27.00 | 1.000 | 202.0 | 764.6 |
| 4 ft | 64.00 | 2.370 | 478.8 | 1,812.3 |
| 5 ft | 125.00 | 4.630 | 935.1 | 3,539.6 |
| 6 ft | 216.00 | 8.000 | 1,615.8 | 6,116.4 |
The calculator shows cubic feet to two decimals, so a 6-inch cube displays as 0.13 ft³.
Where cubes come up on a job
- Picturing bulk orders: One cubic yard of soil or stone is a 3 ft cube. Two yards is two of them side by side.
- Concrete test cubes: Labs in many countries crush 150 mm cubes (about 6 inches) to check strength. US labs mostly use cylinders instead.
- Square planters and bins: A 2 ft cube planter needs 8 cubic feet of potting mix to fill to the rim.
- Water and storage cubes: Square tanks and IBC totes are close to cubes. Measure all three sides; most totes are not perfect cubes.
Working backward from a volume
Sometimes you know the volume and need the side, for example a square bin that must hold 2 cubic yards of compost. Convert to cubic feet first (2 × 27 = 54), then take the cube root. The cube root of 54 is about 3.78, so a bin 3 ft 9.4 in on each side holds it. Check by entering 3.78 into the calculator: it returns 54.01 cubic feet.
How to measure
- Measure all three edges even if the object looks like a cube. If any differ by more than about half an inch, use the rectangular prism tool.
- Use inside dimensions for containers. Walls take up space you cannot fill.
- Convert inches first. Enter 30 inches as 2.5 ft, not 30.
- Fill height matters. A planter filled 2 inches below the rim is a box, not a cube. Use the actual fill depth.
Common mistakes
- Squaring instead of cubing. Side × side is area. A cube needs the side a third time.
- Mixing inches and feet. Entering 24 for a 24-inch cube gives 13,824 cubic feet instead of 8.
- Dividing cubic feet by 9. Nine converts square feet to square yards. Cubic feet to cubic yards is 27.
Related calculators
For boxes with three different sides, use the rectangular prism volume calculator. The volume calculator covers other shapes, and the cubic feet to gallons calculator converts any cubic-foot figure on its own.
Frequently asked questions
What's the formula for cube volume?
Volume equals the side length cubed: V = s³, or side × side × side. Because every edge of a cube is the same, one measurement is enough. A 2 ft cube is 2 × 2 × 2 = 8 cubic feet.
How is a cube different from a rectangular prism?
A cube is a rectangular prism whose length, width, and height are all equal. If one side differs by even an inch, use the rectangular prism volume calculator, which takes three separate measurements.
Why does volume increase so fast when the side length grows?
Because the side is used three times. Doubling the side multiplies the volume by 2 × 2 × 2 = 8. A 2 ft cube holds 8 cu ft while a 4 ft cube holds 64 cu ft. Adding just 6 inches to a 3 ft cube (to 3.5 ft) raises it from 27 to 42.9 cu ft, almost 60% more.
How many gallons does a cube hold?
Multiply cubic feet by 7.48052. A 4 ft cube is 64 cu ft, which holds 478.8 gallons or 1,812.3 liters. A 1 ft cube holds 7.5 gallons.
How do I measure a cube in inches?
Divide the inches by 12 first, then enter feet. An 18-inch cube is 1.5 ft, which gives 3.38 cu ft. For a small cube you can also cube the inches and divide by 1,728: 18 × 18 × 18 = 5,832 cubic inches, and 5,832 ÷ 1,728 = 3.375 cu ft.
Estimates only. Verify quantities with your supplier before purchasing.