Cubic feet calculator, for a box, a list or any unit.

A cubic feet calculator finds how much space something takes up in cubic feet: the length times the width times the height of a box, room or load, with the answer also in cubic inches, cubic yards, cubic metres, litres and US gallons. It handles a single box, cylinder, cone, sphere, pyramid, wedge or tapered cylinder, adds up a list of boxes for a move, storage unit or shipment, tells you how many boxes of one size fit in a space, and converts any other volume unit to cubic feet.

How to use the cubic feet calculator

1. Choose One shape, List of boxes, How many boxes fit? or Convert to cubic feet.
2. For one shape, pick it in Shape, type its sizes, choose the Size unit and how many you have. Inches, feet, yards, metres, centimetres and millimetres all work. Area times depth is for a floor, bed or slab where you know the area, for example 100 square feet and a depth of 2 feet.
3. For a list, type one box per line, such as 24 x 18 x 18 in x 10 (that is ten boxes of 24 by 18 by 18 inches). A line can carry its own unit, and a unit-free line uses the one you pick below.
4. For a fit, type the inside size of the space and the outside size of one box, each with its own unit. Untick Keep boxes upright if the boxes may lie on their side.
5. To convert, type the Volume and pick what it is in now.
6. The first card is always cubic feet, or the box count. Copy result copies it with the other units, and Copy link keeps your inputs.

The formula and the units

For a box, volume = length × width × height. If all three are in feet, the answer is in cubic feet. If they are in inches, multiply them to get cubic inches and divide by 1,728, because one cubic foot is 12 × 12 × 12 cubic inches. A cubic yard is 27 cubic feet (3 × 3 × 3). One foot is exactly 0.3048 metres, so one cubic foot is exactly 0.028316846592 cubic metres, or about 28.3168 litres. A US gallon is 231 cubic inches, so a cubic foot holds 7.4805 US gallons (1,728 ÷ 231). The values come from the international foot and the US gallon as defined in NIST Handbook 44, Appendix C, checked 24 Oct 2026.

Worked example: a box in feet

A box 6 ft long, 4 ft wide and 3 ft high holds 6 × 4 × 3 = 72 cubic feet. That is 72 ÷ 27 = 2.6667 cubic yards, 2.0388 cubic metres, 2,038.8 litres or about 538.6 US gallons. A room 12 ft by 10 ft with an 8 ft ceiling is 960 cubic feet, or 35.56 cubic yards.

Worked example: boxes in inches

A moving box of 24 × 18 × 18 inches is 7,776 cubic inches. Divide by 1,728 and you get 4.5 cubic feet. Ten of them are 45 cubic feet. The list option does this for every line and adds the lines: 10 boxes of 24 × 18 × 18 in (45 ft³), one box of 48 × 24 × 24 in (16 ft³) and four boxes of 3 × 2 × 2 ft (48 ft³) come to 109 cubic feet.

How many boxes fit in a space

Adding up volumes tells you how much space the boxes take, but not whether they fit. The fit mode tries each way of turning the box and counts how many fit in a neat grid, all turned the same way. In a space 10 ft by 10 ft by 8 ft (120 × 120 × 96 in), boxes of 24 × 18 × 18 in fit 5 along the length, 6 across and 5 high, which is 150 boxes. They take 150 × 4.5 = 675 of the 800 cubic feet, 84.4 percent. Turning matters for other boxes. A box of 30 × 20 × 20 in standing upright gives 4 × 6 × 4 = 96 boxes, but laid down with the 30 in side upright it gives 6 × 6 × 3 = 108 boxes. If the box must stay upright, leave the tick on and the page only turns it around the vertical.

The count is a safe plan for a neat stack, not a limit. Mixing two ways of turning can fit more, and leaving space for a door, a walkway or a pallet fits fewer. Use the outside size of the box and the inside size of the space.

Cylinders, cones, spheres and other shapes

A cylinder 3 ft across and 4 ft tall has a volume of π × 1.5² × 4 = 28.2743 cubic feet, such as a round tank or a barrel. A cone of the same size has one third of that, 9.4248. A sphere 2 ft across is π × 2³ ÷ 6 = 4.1888 cubic feet. A pyramid with a 6 ft by 6 ft base and 6 ft height is 6 × 6 × 6 ÷ 3 = 72 cubic feet, one third of the 216 cubic foot box around it. A wedge with a triangle of base 3 ft and height 4 ft, 5 ft long, is ½ × 3 × 4 × 5 = 30 cubic feet. A tapered cylinder 4 ft across at the bottom, 2 ft across at the top and 3 ft high is π × 3 × (2² + 2 × 1 + 1²) ÷ 3 = 21.99 cubic feet.

Converting to cubic feet

Common problems

• Mixed units. Measure all three sides in the same unit before multiplying. Feet times inches gives nonsense. In the list, write the unit on the line.
• Inside and outside size. A box that you fill is measured inside, and one that you stack is measured outside. Boxes leave gaps when they stack, so plan extra room.
• Cubic feet and square feet. Square feet measure a flat area. For a floor with a depth, multiply by the depth to get cubic feet, or use Area times depth.
• Pyramids and cones. They hold one third of the box or cylinder around them, not half.

For more shapes see the area and volume calculator. For cement and stone, use the concrete calculator and the gravel calculator, and for other units the unit converter.