Cubic Feet Calculator
Free, with no sign up. Calculations run on your device; your entries stay in this browser.
Cubic feet measure volume, not floor area. For a box, multiply length × width × height in feet; with inches divide the resulting cubic inches by 1,728. Select a solid and enter its dimensions in a single length unit. For circular solids, enter radius rather than diameter. Pyramid means a rectangular base; height is perpendicular to that base, not the slant height.
Your result
Cube: V = side³. Box: V = lwh. Cylinder: V = πr²h. Cone: V = πr²h/3. Sphere: V = 4πr³/3. Rectangular pyramid: V = lwh/3. 1 m³ = 1,000 L.
Primary source: Massachusetts DESE mathematics reference sheet (solid volume formulas); NIST SP 811 conversion factors (1 foot = 0.3048 m; 12 inches = 1 foot).
Worked example
A box 3 ft long, 4 ft wide and 5 ft high has 3 × 4 × 5 = 60 ft³. A 24 in × 12 in × 6 in box has 1,728 in³ ÷ 1,728 = 1 ft³. One cubic foot is exactly 0.028316846592 m³, or 28.316846592 litres.
For concrete quantities and bag counts, use the Concrete Calculator.
How to use this tool
Start with a box in feet, enter length, width and height, then select Calculate. Change the dimension unit or solid when needed; cubic feet always appear first.
Frequently asked questions
How do I calculate cubic feet from inches?
Multiply all three box dimensions in inches, then divide by 1728. Choose Inches in the controls and the calculator performs that conversion.
What is the difference between square and cubic feet?
Square feet measure area from two dimensions. Cubic feet measure volume from three dimensions; height or depth is required for a box.
Can I calculate a cylinder?
Yes. Select Cylinder and enter radius and perpendicular height in the same unit. Radius is half the diameter. The result shows cubic feet first.