Cubic Feet Calculator

Quick Answer

Last updated: 10 November 2026 ·How we calculate this: length × width × height, converted to feet

How This Cubic Feet Calculator Works

Cubic feet measure volume: how much space something fills or holds. Pick a shape, choose the unit you measured in and enter the sizes. The calculator converts every size to feet, works out the volume and shows it in cubic feet, cubic inches, cubic yards, cubic meters, liters and US gallons. Enter a quantity to total several identical boxes.

How to Use the Cubic Feet Calculator

1. Choose the shape: box or room, cylinder or sphere.
2. Pick the unit you measured in.
3. Enter the sizes, using decimals for mixed feet and inches.
4. Enter how many identical items there are.
5. Press Calculate to see cubic feet and the other units.

Cubic Feet Formulas

• Box or room: length × width × height
• Cylinder: π × (diameter ÷ 2)² × height
• Sphere: 4/3 × π × (diameter ÷ 2)³
• Inches to cubic feet: cubic inches ÷ 1,728
• Cubic feet to gallons: × 7.48052 (1 US gallon = 231 cubic inches)

Key Terms

• Cubic foot: the volume of a cube 1 ft on each side, 1,728 cubic inches.
• Cubic yard: 27 cubic feet, the usual unit for soil, gravel and concrete.
• Volume: the amount of three-dimensional space something fills.
• Liter: a metric unit of volume; 1 cubic foot is about 28.32 liters.
• US gallon: 231 cubic inches; 1 cubic foot is about 7.48 gallons.

Worked Example

A round water tank is 3 ft across and 4 ft tall. How much does it hold?

• Radius = 3 ÷ 2 = 1.5 ft
• Volume = π × 1.5² × 4 = 28.27 cu ft
• In gallons: 28.27 × 7.48052 = 212 US gallons
• In liters: 28.27 × 28.3168 = 801 liters

Real-Life Examples

• Moving boxes: a 24 × 18 × 18 inch box is 4.5 cu ft, so 20 of them fill 90 cu ft.
• Room air volume: a 12 × 14 ft room with an 8 ft ceiling holds 1,344 cu ft of air, which you need for CFM and BTU sizing.
• Raised bed soil: a bed 8 ft × 4 ft × 1 ft needs 32 cu ft, which is 1.19 cubic yards or about 16 bags of 2 cu ft soil.
• Fridge size: inside sizes of 28 × 26 × 60 inches give 25.3 cu ft.

Cubic Feet vs Square Feet

• Square feet measure flat area: length × width. Use them for flooring, paint and land.
• Cubic feet measure volume: length × width × height. Use them for storage, soil, concrete and air.
• Turning one into the other: multiply square feet by a height or depth in feet to get cubic feet.

Cubic Feet Conversions

Inside vs Outside Measurements

Use inside sizes when you want to know how much a container, fridge or room can hold, and outside sizes when you want to know how much space an item takes up, for example in a moving truck or storage unit. Walls, insulation and packaging can make the two numbers very different.

For irregular spaces, such as an L-shaped room, split the space into boxes, work out each one and add them together.

Common Mistakes to Avoid

• Dividing inches by 12 only once. Cubic inches to cubic feet needs ÷ 1,728, not ÷ 12.
• Mixing feet and inches. Convert 4 ft 6 in to 4.5 ft before multiplying.
• Using the diameter as the radius. Halve the diameter for cylinders and spheres.
• Confusing square and cubic feet. Volume needs a third size: height or depth.
• Measuring outside when you need capacity. Use inside sizes for what something holds.

Frequently Asked Questions

References & Sources