Cubic Feet Calculator
Calculate the volume in cubic feet of a box or room, cylinder, sphere, or a whole list of moving boxes. Enter dimensions in feet, inches, cm or m and get instant conversions to in³, m³, liters and gallons.
Calculate Cubic Feet — Box, Room, Cylinder, Sphere or a List of Boxes
Cubic Feet Formula
Where:
- \(V\) — volume in cubic feet (ft³)
- \(L\), \(W\), \(H\) — length, width and height, expressed in feet
- \(D\) — diameter, expressed in feet
- \(\pi \approx 3.14159\)
The box formula multiplies the three inside dimensions together; the cylinder formula uses the circular cross-section area times the height; the sphere formula equals \(\tfrac{4}{3}\pi r^3\) rewritten in terms of the diameter.
Cubic Feet – Calculation Example
Example: a box measures 3 ft long, 2 ft wide and 1 ft 6 in high (the calculator's default values).
\[ H = 1\ \text{ft} + \frac{6\ \text{in}}{12} = 1.5\ \text{ft} \]
\[ V = 3 \times 2 \times 1.5 = 9\ \text{ft}^3 \]
Result: \(V = 9\) ft³, which is the same as 15,552 in³, 0.33333 yd³, 0.25485 m³, 254.85 liters or 67.325 US gallons.
How to Use the Cubic Feet Calculator
- Open the What do you want to calculate? dropdown and pick a mode: rectangular box or room, cylinder, sphere, a multi-item box list, or the quick volume converter. Any section you are not using is hidden automatically.
- For a box or room, enter Length (L), Width (W) and Height (H), choosing a unit for each (in, ft, yd, cm or m). If a dimension is given as feet plus inches, set the unit to ft and type the leftover inches in the + Inches (with ft) field that appears below it.
- For a cylinder, enter Diameter (D) and Height (H); for a sphere, just the diameter. The same feet-plus-inches helper works here too.
- For a move or shipment, choose Multi-item list and type one line per box size in the Box list field:
L W H [qty]— for example24 18 16 2means two boxes of 24 × 18 × 16. Leave off the quantity for a single box, up to 10 lines. Then set Unit for all list dimensions (in, ft, yd, cm or m). - For a plain unit conversion, choose Quick converter, type the Volume and its unit (ft³, in³, yd³, m³, liters or US gallons).
- Read the result under Total volume in cubic feet, plus instant conversions to in³, yd³, m³, liters and US gallons. For boxes, the Dimensional (shipping) weight in pounds is also shown, and the multi-item mode adds an item-by-item breakdown table.
What a Cubic Foot Represents
A cubic foot is the volume of a cube that is exactly one foot (12 inches) on each side: \(1 \times 1 \times 1\) ft. Because it is a three-dimensional unit, one cubic foot contains \(12^3 = 1{,}728\) cubic inches, and 27 cubic feet make up one cubic yard. In metric terms, \(1\ \text{ft}^3 \approx 28.32\) liters or \(0.02832\ \text{m}^3\), since one foot is defined as exactly 0.3048 m.
Cubic feet show up everywhere volume matters in everyday life: the capacity of a refrigerator, a shipping box, a planter, a concrete pour, or the airflow rating of an HVAC system (CFM is literally cubic feet per minute). Moving companies and freight carriers quote prices partly by total cubic feet, and soil, mulch and concrete are often sold by the cubic yard — which is just 27 ft³.
Because the calculator converts every result to common units at once, you can check a figure against a supplier's quote without doing arithmetic by hand. For example, if you need to fill a raised bed described in liters, you can verify it equals about 14.4 ft³ and decide whether two cubic-yard bags will cover it.
Note the dimensional weight figure for boxes: parcel carriers compute it as \(L \times W \times H\) in inches divided by 139, and bill whichever is greater — dimensional or actual weight. A light but bulky box can therefore cost as if it weighed far more.
Tips, Assumptions and Limitations
- All dimensions are treated as exact, and boxes, rooms and cylinders are assumed to be perfect — no allowance is made for wall thickness, packaging voids, asymmetries or irregular shapes.
- For rooms, include only the space you actually want to measure: exclude built-in furniture for storage estimates, or use floor-to-ceiling height only if you truly plan to fill the whole height. Realistic loading never fills a room or truck completely — add a 10–20 % buffer for packing gaps.
- The feet-plus-inches fields convert 12 or more inches automatically (18 in becomes 1 ft 6 in), but for purely inch-based measurements it is simpler to enter each dimension with the in unit selected.
- The dimensional weight uses the standard divisor 139 in³/lb used by most US parcel carriers; express and freight services may use different divisors, so confirm with your carrier before relying on the figure.
- Results are rounded for display: 4 decimals for ft³, 2 decimals for liters and in³. Plan material purchases with a small margin on top.
Handy Conversion Reference
| 1 cubic foot equals… | Value |
|---|---|
| Cubic inches | 1,728 in³ |
| Cubic yards | 0.03704 yd³ (1/27) |
| Cubic meters | 0.02832 m³ |
| Liters | 28.3168 L |
| US gallons | 7.4805 gal |
If you also work with metric plans, the meters to feet converter pairs well with this tool, and the feet and inches calculator handles mixed-unit arithmetic. For silos, aquariums and round tanks, see the tank volume calculator, or use the rainfall volume calculator to estimate water collected over an area in ft³.
Frequently Asked Questions
How do I calculate cubic feet from measurements in inches?
Convert each dimension to feet first by dividing the inches by 12, then multiply all three together. For a 36 in × 24 in × 18 in box: 3 ft × 2 ft × 1.5 ft = 9 ft³. Alternatively, multiply the three inch values and divide the result by 1,728 (because \(12^3 = 1728\)): 36 × 24 × 18 = 15,552 in³ ÷ 1,728 = 9 ft³. Both routes give the same answer.
How many cubic feet are in a cubic yard of soil, mulch or concrete?
One cubic yard equals 27 cubic feet (3 ft × 3 ft × 3 ft). So a 2-cubic-yard delivery of mulch covers 54 ft³, which would fill, for example, a raised bed of about 8 ft × 4 ft × 1.7 ft. Landscape suppliers often round to whole or half yards, so calculating your exact ft³ first helps you decide whether to order more or less.
What is the difference between cubic feet and square feet?
Square feet measures area (two dimensions), while cubic feet measures volume (three dimensions). A floor that is 10 ft × 12 ft has an area of 120 ft², but the room's volume is 120 ft² multiplied by the ceiling height — 9 ft ceilings give 1,080 ft³. You cannot convert between the two without knowing a height or depth: ft³ = ft² × depth in feet.
How do I calculate cubic feet of an L-shaped or irregular room?
Split the shape into simple rectangles, calculate each volume separately, then add them together. For an L-shaped room, divide it into two rectangular sections and compute L × W × H for each. For sloped ceilings, use the average height as a reasonable estimate, or calculate the lower section and the wedge above it as two pieces. The result slightly overstates usable space, so keep a 10–20 % buffer for storage planning.
Why do I get the wrong answer when dimensions are in different units?
Mixing units without converting is the most common mistake. If length is 3 ft and width is 30 inches, you cannot multiply 3 × 30 directly — first convert 30 in to 2.5 ft, giving 7.5 ft² per foot of height. Set each dimension's unit independently in the calculator (in, ft, yd, cm or m), or use the feet-plus-inches helper field, and the conversion happens for you.
How does the gallons conversion work — and which gallon is used?
The results use US gallons: \(1\ \text{ft}^3 \approx 7.48\) US gal. A UK (imperial) gallon is about 20 % larger, so 1 ft³ is only about 6.23 imperial gallons — always check which gallon a spec sheet means. For aquariums or tanks, the multi-item list is not needed; just use the box or cylinder mode and read the gallon output directly.
How many moving boxes fit in a standard cargo space or truck?
Compare total ft³: a typical 20 ft U-Haul truck holds about 1,016 ft³, a cargo van roughly 400–450 ft³, and an SUV trunk around 80–100 ft³. Add up your boxes with the multi-item mode, then divide by the vehicle's capacity. Because boxes never stack perfectly and irregular items fill gaps, assume you can realistically use about 70–85 % of the rated volume.