Cubic Feet Calculator: Find Volume from Dimensions

A cubic feet calculator finds the volume of a space or object in cubic feet from its length, width, and height. Enter all three dimensions in feet to get the volume; the calculator can also convert the result to cubic inches, cubic yards, or cubic metres.

Formula

For a rectangular space, multiply its length by its width by its height:

Volume = length × width × height

• Length is the inside or measured length in feet (ft).
• Width is the corresponding width in feet (ft).
• Height is the vertical dimension in feet (ft).
• Volume is in cubic feet (ft³), also written as cu ft or ft³.

The conversion outputs use 1 cubic foot = 1,728 cubic inches, 27 cubic feet = 1 cubic yard, and 1 cubic foot = 0.028316846592 cubic metres. These are unit conversions; they do not change the dimensions or the shape assumed by the calculation.

Worked Example

Using the calculator’s default dimensions—10 ft long, 8 ft wide, and 6 ft high:

1. Multiply the length and width: 10 × 8 = 80 square feet.
2. Multiply that area by the height: 80 × 6 = 480 ft³.
3. Convert to cubic inches: 480 × 1,728 = 829,440 in³.
4. Convert to cubic yards: 480 ÷ 27 = 17.777…, or 17.778 yd³ to three decimal places.
5. Convert to cubic metres: 480 × 0.028316846592 = 13.592…, or 13.592 m³ to three decimal places.

The main result is 480 cubic feet. The extra results express the same volume in other units; they are not additional space.

How Cubic Feet Measure Volume

A cubic foot is the volume of a cube with sides one foot long. Since one foot is 12 inches, that cube contains 12 × 12 × 12 = 1,728 cubic inches. The word “cubic” matters: feet alone measure length, while square feet measure area and cubic feet measure three-dimensional space.

Volume calculations are useful for estimating the space inside a room, storage area, box, tank, or other roughly rectangular object. They can also help compare capacities or estimate the amount of a material needed to fill a rectangular space. The calculation describes the geometric volume, not necessarily the usable capacity: walls, fittings, contents, and fill limits may reduce what actually fits.

Using the Calculator and Measuring

Measure the three dimensions in feet, then enter them in the matching fields. For an interior space, measure between the surfaces that bound the usable space rather than relying on outside dimensions. Keep measurements in a consistent unit before multiplying.

• Measurements in inches: divide each measurement by 12 to convert it to feet. For example, 30 inches is 2.5 feet.
• Measurements in metres: convert each dimension to feet by multiplying by approximately 3.28084, or calculate in cubic metres and convert the final result.
• Mixed measurements: convert them all to the same unit first. Multiplying feet by inches directly does not produce cubic feet.
• Irregular spaces: divide the area into rectangular sections, calculate each section’s volume, and add the results. Subtract separately measured empty or obstructed sections if the desired result is net volume.

For a room with a recess or an L-shaped floor plan, a single length × width × height calculation may count space that is not present. Breaking the shape into simple boxes avoids that problem. The sections should not overlap, or the shared volume will be counted twice.

Choosing the Right Shape and Understanding Limits

The three-dimension formula applies to rectangular prisms: shapes with rectangular faces and straight, parallel sides. A perfect fit is not required for a rough estimate, but sloping walls, rounded corners, uneven floors, and irregular objects make the result less exact.

Other shapes require different formulas. A cylinder’s volume is π × radius² × height; a sphere’s is 4/3 × π × radius³. For a room or object with mixed shapes, calculate each simple component using its appropriate formula and combine the volumes. For an uneven or irregular container, measured capacity or a more detailed geometric model may be more suitable than treating it as a box.

A common misconception is that multiplying the floor area by the height always gives the exact amount of usable or fillable space. It gives the geometric volume only when the space has a consistent rectangular footprint and height. A material’s packing, settling, air gaps, or container shape can make the quantity needed differ from the mathematical volume.

Common Mistakes and Rounding

• Confusing area with volume: length × width gives square feet. Multiply by height to get cubic feet.
• Mixing units: convert every dimension to feet before using the cubic-feet formula.
• Using outside dimensions: thick walls or a lid can make exterior measurements overstate interior capacity.
• Rounding too early: keep the original measurements through the calculation, then round the final value to a useful precision.
• Assuming a capacity is exact: a nominal container size or a rough tape measurement may not describe the exact usable volume.

The calculator displays cubic feet to two decimal places, cubic yards and cubic metres to three, and cubic inches as a whole number. These display choices affect rounding, not the underlying formula. If the input measurements are approximate, extra decimal places do not make the estimate more precise.

Frequently Asked Questions

How do I calculate cubic feet?
Multiply length × width × height, with all three measurements in feet. The result is in cubic feet.

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

How do I convert cubic inches to cubic feet?
Divide cubic inches by 1,728. For example, 3,456 in³ ÷ 1,728 = 2 ft³.

Can I calculate cubic feet from inches?
Yes. Convert each dimension from inches to feet by dividing by 12, then multiply the converted dimensions. Alternatively, multiply the three measurements in inches and divide by 1,728 to get cubic feet.

How do I find the cubic feet of an irregular room?
Divide it into non-overlapping rectangular sections, calculate each section’s volume, and add them. Use a suitable shape formula for curved or sloping sections rather than forcing them into a rectangular calculation.

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in length | Length | ft | 10 | 0
in width | Width | ft | 8 | 0
in height | Height | ft | 6 | 0
out volume | Volume | ft³ | length * width * height | 2
out inches | Volume | in³ | length * width * height * 1728 | 0
out yards | Volume | yd³ | length * width * height / 27 | 3
out metric | Volume | m³ | length * width * height * 0.028316846592 | 3