Cubic Feet Calculator: L x W x H in Seconds

A cubic feet calculator computes the volume of a rectangular space (like a box, room, or shipping crate) from its length, width, and height in feet, giving you the result in cubic feet (ft³). You enter the three dimensions, and the calculator multiplies them together to return the total volume—the same math as the formula Volume = Length × Width × Height.

Formula

The core formula is straightforward:

Volume (V) = Length (L) × Width (W) × Height (H)

Where:

• V = volume in cubic feet (ft³)
• L = length in feet (ft)
• W = width in feet (ft)
• H = height in feet (ft)

If your measurements are in inches, centimeters, or meters, you must convert them to feet first. The calculator above does that conversion for you when you use the unit options, but the underlying math is always: multiply the three dimensions (all in feet) to get cubic feet.

Worked Example

Using the default values from the calculator above:

1. Length = 10 ft
2. Width = 5 ft
3. Height = 4 ft
4. Multiply: 10 × 5 × 4 = 200

The volume is 200 cubic feet. The calculator also shows that this equals 345,600 cubic inches (200 × 1,728) and approximately 5.66 cubic meters (200 × 0.0283168).

Why Cubic Feet Matter

Cubic feet is the standard unit of volume in the United States for many practical applications. You’ll encounter it when:

• Shipping and freight: Carriers charge by dimensional weight, which is based on cubic volume, not just weight.
• Moving and storage: Rental trucks and storage units are sized in cubic feet (e.g., a 10×10×8 unit is 800 ft³).
• Home improvement: Concrete, soil, mulch, and gravel are often sold by the cubic foot or cubic yard (1 yd³ = 27 ft³).
• HVAC and appliances: Room volume helps determine the correct air conditioner size or ceiling fan rating.
• Aquariums and pools: Water volume in cubic feet can be converted to gallons (1 ft³ ≈ 7.48 gallons).

Knowing the cubic footage of a space or object lets you plan purchases, estimate costs, and avoid over- or under-ordering materials.

How to Measure Correctly

Accurate measurements are the difference between a useful answer and a wasted trip to the store. Follow these steps:

1. Use a tape measure or laser measure, not a ruler, for anything larger than a shoebox.
2. Measure the interior dimensions of a container or room, not the exterior, unless you’re calculating the space the object occupies.
3. Measure to the nearest inch for most projects; for shipping, measure to the nearest 0.1 inch if possible.
4. If the shape isn’t a perfect rectangle, break it into rectangular sections, calculate each volume, and add them together.
5. For irregular objects (like furniture), measure the widest, longest, and tallest points to get an approximate bounding box.

When measuring a room, remember to account for obstructions like built-in shelves or sloped ceilings—you may need to subtract those volumes for accurate material estimates.

Common Mistakes and How to Avoid Them

Even with a simple formula, errors creep in. The most frequent ones:

• Mixing units: The classic error. If you measure length in feet, width in inches, and height in centimeters, the result is meaningless. Always convert to one unit first.
• Forgetting to convert inches to feet: 12 inches = 1 foot. A box that is 24 inches × 12 inches × 12 inches is 2 × 1 × 1 = 2 ft³, not 24 × 12 × 12 = 3,456 ft³.
• Rounding too early: If your dimensions are 5.5 ft, 6.2 ft, and 4.8 ft, multiply them all first (5.5 × 6.2 × 4.8 = 163.68 ft³) before rounding. Rounding each dimension to 6, 6, and 5 gives 180 ft³—a 10% error.
• Confusing cubic feet with square feet: Square feet is area (L × W); cubic feet is volume (L × W × H). A 10×10 room is 100 ft², but if it has 8-foot ceilings, it’s 800 ft³.
• Ignoring the difference between US and imperial gallons: If you convert cubic feet to gallons, note that 1 ft³ = 7.48 US gallons but 6.23 imperial gallons. The calculator above uses US gallons.

Double-check your measurements twice, especially for expensive materials like concrete or shipping charges.

Converting to Other Volume Units

Sometimes you need cubic feet in a different unit. Here are the most common conversions:

• 1 cubic foot = 1,728 cubic inches (since 12³ = 1,728)
• 1 cubic foot = 0.0283168 cubic meters
• 1 cubic foot = 7.48052 US gallons
• 1 cubic yard = 27 cubic feet
• 1 cubic foot = 28.3168 liters

To convert from cubic feet to another unit, multiply by the factor above. To convert to cubic feet, divide by that factor. For example, to convert 500 liters to cubic feet: 500 ÷ 28.3168 ≈ 17.66 ft³.

Limitations of the Formula

The L × W × H formula assumes a perfect rectangular prism. In reality:

• Round or tapered objects: A cylinder’s volume uses Ï€r²h, not L×W×H. A cone or pyramid needs its own formula (â…“ × base area × height).
• Irregular shapes: For a rock or a piece of furniture with curves, the bounding-box method overestimates volume. Use water displacement for small irregular objects.
• Sloped ceilings or angled walls: The formula gives the volume of a box that would contain the space, not the actual usable volume. For a room with a sloped ceiling, calculate the triangular portion separately.
• Material compaction: For soil, mulch, or gravel, the volume you calculate is the “looseâ€� volume. When compacted, the same weight takes up less space—a fact you should confirm with your supplier.

For those cases, use the appropriate geometric formula or a specialized calculator (cylinder, sphere, cone). This calculator is for rectangular prisms only.

Frequently Asked Questions

How do I calculate cubic feet from inches?

Convert each inch measurement to feet by dividing by 12, then multiply the three results. For example, a box that is 24 in × 18 in × 12 in becomes 2 ft × 1.5 ft × 1 ft = 3 ft³. Alternatively, multiply inches first to get cubic inches, then divide by 1,728.

What is the difference between cubic feet and square feet?

Square feet measures area (two dimensions: length × width). Cubic feet measures volume (three dimensions: length × width × height). A 10×10 room is 100 ft², but if the ceiling is 8 feet high, the room’s volume is 800 ft³. You cannot convert directly between them without knowing the third dimension.

How many cubic feet are in a cubic yard?

There are 27 cubic feet in 1 cubic yard. This is because 1 yard = 3 feet, and 3³ = 27. When buying soil, mulch, or concrete, suppliers often quote prices per cubic yard, so divide your cubic feet by 27 to get yards.

How do I calculate the cubic feet of a room for an air conditioner?

Measure the room’s length, width, and ceiling height in feet, then multiply them. For example, a 12 ft × 15 ft room with 8 ft ceilings is 1,440 ft³. Air conditioner sizing (BTU) typically uses square footage, but ceiling height matters for rooms with high or vaulted ceilings—use the cubic footage to adjust.

Can I use this calculator for shipping dimensional weight?

Yes, but note that carriers use a divisor (e.g., 139 for domestic, 166 for international) on the cubic volume in inches. First calculate cubic inches (L×W×H in inches), then divide by the carrier’s divisor to get dimensional weight in pounds. This calculator gives you the raw cubic feet, which you can convert to inches by multiplying by 1,728.

What if my box is not a perfect rectangle?

For irregular shapes, measure the maximum length, width, and height to get a bounding box. This overestimates the true volume but is often what shipping companies use. For precise volume of a cylinder, use πr²h; for a sphere, use (4/3)πr³. This calculator is for rectangular prisms only.

Related

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• Aspect Ratio Converter Calculator: How to Use It
• Aspect Ratio Calculator Inches: Find Screen Size

in l | Length | ft | 10 | 0
in w | Width | ft | 5 | 0
in h | Height | ft | 4 | 0
out vol | Volume | ft³ | l * w * h | 2
out vol_in | Volume (in³) | in³ | l * w * h * 1728 | 0
out vol_m3 | Volume (m³) | m³ | l * w * h * 0.0283168 | 2