Cubic Feet Calculator: Measure Volume from Dimensions

A cubic feet calculator finds the volume of a space or object from its length, width, and height. Enter all three dimensions in feet to get cubic feet; you can also enter inches, or use the conversion factor shown below to convert other units.

Formula

Cubic feet = length × width × height. Use the same unit for every dimension, then multiply the measurements. The calculator’s primary result is cubic feet (ft³); its additional results convert that volume to US liquid gallons and cubic meters.

• Length (l): one side of the space, in feet (ft).
• Width (w): the side perpendicular to the length, in feet.
• Height (h): the vertical dimension, in feet.
• Cubic feet (cf): volume, in cubic feet.
• US gallons (gal): cf × 7.48052. This is a volume conversion, not an Imperial-gallon conversion.
• Cubic meters (m³): cf × 0.0283168.

In symbols, V = l × w × h. A cubic foot is the volume of a cube with sides one foot long. Since one foot is 12 inches, one cubic foot contains 12 × 12 × 12 = 1,728 cubic inches.

Worked Example

Using the calculator’s default dimensions—10 ft long, 10 ft wide, and 8 ft high:

1. Multiply length by width: 10 ft × 10 ft = 100 ft².
2. Multiply by height: 100 ft² × 8 ft = 800 ft³.
3. Convert to US gallons: 800 × 7.48052 = 5,984.42 gal.
4. Convert to cubic meters: 800 × 0.0283168 = 22.65344 m³, or 22.653 m³ to three decimal places.

The main result is 800.00 cubic feet. The area units in the first step become volume units when multiplied by the height.

How to Measure and Use the Result

Measure the inside dimensions when estimating the capacity of a room, cabinet, storage space, or container. For a rectangular space, choose the three dimensions that meet at a corner. If your tape measure gives inches, convert each measurement to feet by dividing by 12 before multiplying. For example, 30 inches is 2.5 feet.

For a practical estimate, use a consistent measurement convention. A room’s inside dimensions estimate usable enclosed volume, while outside dimensions include wall thickness and may overstate the space available inside. For irregularly shaped spaces, divide the shape into simpler sections, calculate each section’s volume, and add the results. Subtract large solid areas only when you need the unoccupied volume rather than the enclosing space’s full capacity.

Cubic feet describe three-dimensional volume; square feet describe two-dimensional area. A floor that measures 10 ft by 10 ft has an area of 100 ft². If its ceiling is 8 ft high, its rectangular volume is 800 ft³. Neither figure alone tells you how much usable storage space there is: shelves, furniture, slopes, or restricted openings can reduce practical capacity.

Conversions and Other Shapes

Common conversions help when a product specification or measurement uses a different unit:

• Inches to cubic feet: multiply cubic inches by 0.000578704, or divide by 1,728.
• Cubic yards to cubic feet: multiply cubic yards by 27.
• Cubic feet to cubic yards: divide cubic feet by 27.
• Cubic feet to cubic meters: multiply by approximately 0.0283168.
• Cubic feet to US gallons: multiply by approximately 7.48052. One US gallon is about 0.133681 ft³.

These conversions change units, not the actual volume. Do not confuse US gallons with Imperial gallons: they are different units. A gallon conversion is also not a weight conversion. How much a volume weighs depends on the material’s density.

For a cylinder, use V = πr²h, where r is the radius and h is the cylinder’s height, with both measurements in feet. For a sphere, use V = (4/3)πr³. If the shape is not a simple solid, splitting it into approximate geometric sections is often more useful than applying the rectangular calculator to dimensions that do not describe the shape.

Common Measurement Mistakes and Limits

• Mixing units: multiplying 10 feet by 24 inches by 8 feet without conversion produces a meaningless result. Convert all dimensions to feet first, or convert all to another common unit.
• Using diameter as radius: for a cylinder, the radius is half the diameter. The rectangular calculator does not apply to cylindrical capacity.
• Rounding too soon: keep the full measured values through multiplication, then round the final answer to a sensible precision. The displayed decimal places do not imply that the measurements are exact.
• Assuming a box fills perfectly: interior shape, wall thickness, packaging, voids, and access openings can change usable capacity.
• Confusing volume with mass: cubic feet indicate space occupied, not pounds or kilograms. A mass estimate requires the material’s density.

The formula assumes straight-sided dimensions and a rectangular-prism shape. Measurement errors in each dimension affect the final volume, and the calculator cannot account for bulges, tapered walls, rounded corners, or obstructions unless you model them separately. Treat results for rough or irregular measurements as estimates.

Frequently Asked Questions

How do I calculate cubic feet from inches?
Convert each dimension from inches to feet by dividing by 12, then multiply length × width × height. Alternatively, multiply the three dimensions in inches and divide the result by 1,728.

How many cubic feet are in a cubic yard?
One cubic yard equals 27 cubic feet, because a yard is 3 feet and 3 × 3 × 3 = 27.

How many gallons are in a cubic foot?
One cubic foot is approximately 7.48052 US gallons. Imperial gallons use a different conversion, so check which gallon unit a specification means.

Can I calculate cubic feet for a round container?
Not with the length × width × height formula alone. For a cylinder, measure its radius and height in feet and calculate π × radius² × height.

Is cubic feet the same as square feet?
No. Square feet measure area, such as a floor’s surface. Cubic feet measure volume and require three dimensions: length, width, and height.

Related

• Square Feet to Square Yards: Formula and Examples
• Feet to Meters: Conversion Formula and Examples
• Cubic Yards to Tons: Formula and Material Examples

in l | Length | ft | 10 | 0
in w | Width | ft | 10 | 0
in h | Height | ft | 8 | 0
out cf | Cubic feet | ft³ | l * w * h | 2
out gal | US gallons | gal | cf * 7.48052 | 2
out m3 | Cubic meters | m³ | cf * 0.0283168 | 3