Cubic feet calculator

What is a cubic foot?

A cubic foot (symbol: ft³ or cu ft) is a unit of volume in the United States customary and British imperial systems. It is the volume of a cube whose edges are each one foot (12 inches, or 0.3048 meters) long. Because it sits between the very small cubic inch and the larger cubic yard, the cubic foot is a practical everyday unit for room capacities, appliance sizes, shipping crates, soil and mulch, refrigerator interiors, and the airflow ratings of fans and HVAC equipment.

This calculator does two jobs at once. First, it computes the volume of a rectangular (box-shaped) space from its length, width, and height. Second, it lets you read that volume back in cubic feet or convert it to other common volume units such as cubic meters, cubic yards, liters, or gallons.

How does the calculator work?

For any rectangular box, the volume is simply the product of its three perpendicular dimensions. Enter the length, width, and height, and the calculator multiplies them together. Each dimension has its own unit selector, so you can mix feet, inches, yards, centimeters, and meters — the tool converts everything to a common base before multiplying. The volume field also has a unit selector, so the same result can be displayed in cubic feet or instantly converted to another unit.

Formula

The volume $V$ of a rectangular space is:

$$V = l \times w \times h$$

where:

• $l$ is the length,
• $w$ is the width,
• $h$ is the height (or depth).

When all three dimensions are given in feet, the result is already in cubic feet. To convert that cubic-foot value to other units, multiply by the appropriate factor:

$$1\ \text{ft}^3 = 0.0283168\ \text{m}^3 = 28.3168\ \text{L} = 7.48052\ \text{US gal} = 6.22884\ \text{UK gal}$$

If a dimension is supplied in inches instead of feet, remember that there are 12 inches in a foot, so $1\ \text{ft}^3 = 12^3 = 1728\ \text{in}^3$.

Worked examples

Example 1: A storage box in feet

A storage box measures 5 ft long, 4 ft wide, and 3 ft high. Its volume is:

$$V = 5 \times 4 \times 3 = 60\ \text{ft}^3$$

So the box holds 60 cubic feet.

Example 2: Converting that volume to cubic meters

To express the same 60 ft³ in cubic meters, multiply by the conversion factor:

$$60 \times 0.0283168 = 1.699\ \text{m}^3$$

Example 3: A one-foot cube in liters and gallons

A perfect cube one foot on each side has a volume of:

$$V = 1 \times 1 \times 1 = 1\ \text{ft}^3$$

That single cubic foot equals about 28.3168 liters, or roughly 7.48 US gallons.

Example 4: Dimensions given in inches

A package measures 12 in × 12 in × 12 in. Since 12 inches equals 1 foot, each side is one foot, so:

$$V = 1 \times 1 \times 1 = 1\ \text{ft}^3$$

The result matches the one-foot cube above — a useful sanity check when mixing units.

Practical notes

1. The length × width × height formula only applies to rectangular (box-shaped) spaces. For cylinders, cones, or irregular shapes, use a dedicated volume tool.
2. Mixing units is fine — the calculator converts each dimension before multiplying — but double-check the unit selectors if a result looks too large or too small.
3. When ordering bulk materials such as soil, gravel, or concrete, cubic feet and cubic yards are common; remember that 1 cubic yard equals 27 cubic feet.
4. For liquids, convert to gallons or liters; confirm whether a US gallon or a UK (imperial) gallon is required, since they differ by about 20%.

Frequently asked questions

How do I calculate cubic feet from length, width, and height?

Multiply the three dimensions together when they are all in feet: cubic feet = length (ft) × width (ft) × height (ft). For a 5 ft × 4 ft × 3 ft space that is $5 \times 4 \times 3 = 60\ \text{ft}^3$.

How do I convert inches to cubic feet?

If your dimensions are in inches, you can divide each one by 12 to get feet first, or compute the volume in cubic inches and divide by 1728, because $1\ \text{ft}^3 = 1728\ \text{in}^3$.

How many gallons are in a cubic foot?

One cubic foot holds about 7.48052 US gallons, or about 6.22884 UK (imperial) gallons.

How many liters are in a cubic foot?

One cubic foot equals approximately 28.3168 liters.