Use this cubic feet calculator to find the volume of a box, room, cylinder or triangular prism, or convert a known volume into cubic feet. Results also show cubic inches, cubic yards, cubic metres, litres and U.S. liquid gallons for easier planning and comparison.
Calculate Cubic Feet and Convert Volume
Choose a shape or known-volume conversion, enter positive measurements and review the complete volume breakdown.
What Is a Cubic Foot?
A cubic foot is a unit of volume equal to a cube that measures one foot long, one foot wide and one foot high. Because one foot contains 12 inches, one cubic foot contains 12 × 12 × 12, or exactly 1,728 cubic inches.
Volume measures three-dimensional space. It is different from length, which uses feet, and area, which uses square feet. Cubic feet are commonly used for rooms, appliances, storage, shipping, soil, mulch, airflow and container capacity.
1 cubic foot = 1 ft × 1 ft × 1 ft = 1,728 in³
How to Calculate Cubic Feet
For a rectangular space, multiply its length, width and height after expressing all three dimensions in the same unit. If the measurements are already in feet, the product is directly in cubic feet.
Cubic feet = length (ft) × width (ft) × height (ft)
- Identify the solid shape you are measuring.
- Measure every required dimension using the same linear unit.
- Apply the correct volume formula.
- If necessary, convert the calculated volume to cubic feet.
- Round only after completing the calculation.
Important: Do not multiply mixed units. Convert, for example, 6 inches to 0.5 feet before multiplying it by measurements stated in feet.
Cubic Feet Formulas by Shape
Rectangular box or room
Multiply the three inside dimensions. This works for rectangular rooms, cartons, cabinets, trailers and containers. For usable capacity, measure the interior rather than exterior dimensions.
Cylinder
Divide the diameter by two to obtain the radius, square the radius, multiply by π and then multiply by the cylinder height or length. The same formula works whether the cylinder is standing upright or lying horizontally.
Triangular prism
First find the triangular end area by multiplying its base by its perpendicular height and dividing by two. Multiply that area by the prism length. The triangle height must meet the base at a right angle.
Cubic Feet Conversion Table
The following factors use the international foot and U.S. liquid gallon. Imperial gallons are different and are not used by this calculator.
| 1 cubic foot equals | Exact or displayed value | Conversion from cubic feet |
|---|---|---|
| Cubic inches | 1,728 in³ | ft³ × 1,728 |
| Cubic yards | 0.037037037 yd³ | ft³ ÷ 27 |
| Cubic metres | 0.028316846592 m³ | ft³ × 0.028316846592 |
| Litres | 28.316846592 L | ft³ × 28.316846592 |
| U.S. liquid gallons | 7.4805194805 gal | ft³ × 1,728 ÷ 231 |
Converting Linear Measurements Before Cubing
A linear conversion factor must be applied to each dimension. That is why cubic conversions are the cube of the related length conversion. One yard is three feet, so one cubic yard is 3³, or 27 cubic feet.
- Inches to feet: divide every dimension by 12, then multiply.
- Yards to feet: multiply every dimension by 3, then multiply.
- Centimetres to feet: divide every dimension by 30.48.
- Metres to feet: divide every dimension by 0.3048.
The calculator performs these linear conversions internally before applying the selected shape formula.
Cubic Feet Calculation Examples
Example 1: room volume
A rectangular room is 10 feet long, 8 feet wide and 9 feet high.
Example 2: cylinder
A cylinder with a 2-foot diameter has a 1-foot radius. If it is 5 feet long, its volume is π × 1² × 5 = about 15.708 cubic feet.
Example 3: triangular prism
A prism has a triangular end 4 feet wide and 3 feet high, plus a length of 10 feet. Its volume is ½ × 4 × 3 × 10 = 60 cubic feet.
Example 4: cubic yards to cubic feet
Because one cubic yard equals 27 cubic feet, 2.5 cubic yards equals 2.5 × 27 = 67.5 cubic feet.
Cubic Feet vs. Square Feet
Square feet measure two-dimensional area, while cubic feet measure three-dimensional volume. A floor measuring 10 by 8 feet covers 80 square feet. Adding a 9-foot height produces a room volume of 720 cubic feet.
Practical Uses and Measurement Limits
Cubic feet can help compare room size, storage space, appliance capacity, package volume and simple material quantities. However, the geometric result is not automatically the amount of material to buy or the usable capacity of a product.
- Use inside dimensions for storage or liquid capacity.
- Use consistent reference points when measuring an irregular room.
- Divide complex shapes into smaller regular solids and add their volumes.
- Allow for voids, compaction, waste, wall thickness and manufacturer requirements.
- Confirm shipping, construction and product-order quantities with the relevant supplier or professional.
Measurement precision limits result precision. If dimensions are measured only to the nearest inch, displaying many decimal places does not make the underlying estimate more accurate.
Related Calculators and References
Use the roof pitch calculator for roof slope and simple gable geometry. Browse the Global Calculators directory or explore more free financial calculators and money tools from 1Dollars.
Conversion factors were checked against the NIST Guide to the SI, Appendix B and its conversion-factor table.
Methodology reviewed: July 19, 2026
Cubic Feet Calculator FAQs
How do I calculate cubic feet?
For a rectangular object or room, multiply length by width by height after expressing all three dimensions in feet. Other shapes require their own volume formulas.
How many cubic inches are in a cubic foot?
There are exactly 1,728 cubic inches in one cubic foot because 12 × 12 × 12 equals 1,728.
How many cubic feet are in a cubic yard?
One cubic yard contains exactly 27 cubic feet because one yard equals three feet and 3³ equals 27.
How many litres are in a cubic foot?
One cubic foot equals exactly 28.316846592 litres when based on the international foot.
How many U.S. gallons are in a cubic foot?
One cubic foot is approximately 7.480519 U.S. liquid gallons. This is not the same as an Imperial gallon conversion.
How do I calculate cubic feet from inches?
Multiply the three dimensions in inches and divide the cubic-inch result by 1,728. You can also divide each linear dimension by 12 before multiplying.
How do I calculate cubic feet of a cylinder?
Convert the measurements to feet, divide the diameter by two, and calculate π × radius² × height or length.
Is cubic feet the same as square feet?
No. Square feet measure area using two dimensions. Cubic feet measure volume using three dimensions.
Can I calculate room volume with this tool?
Yes. Choose Box or room, enter the room's inside length, width and height, and select the measurement unit.
Does measured volume equal usable capacity?
Not always. Wall thickness, fixtures, voids, irregular surfaces, fill level and safety allowances can reduce usable capacity.
Calculation notice: This calculator provides mathematical volume estimates for general planning and education. It does not replace product specifications, site measurements, engineering advice, shipping rules or supplier quantity guidance.