Cubic Inch Calculator
A cubic inch calculator multiplies length × width × height in inches, then divides by 1,728 for cubic feet. A 24 × 12 × 6 in box is 1,728 in³, exactly 1 ft³.
How to calculate cubic inches
This cubic inch calculator multiplies length × width × height, all in inches, to give volume in cubic inches. It then divides by 1,728 to show the same volume in cubic feet. The formula is in³ = L × W × H, and ft³ = in³ ÷ 1,728. A box 24 × 12 × 6 inches holds 1,728 cubic inches, which is exactly one cubic foot.
Enter the three inside dimensions in inches. The result shows cubic inches as a whole number and cubic feet to four decimal places.
Why the magic number is 1,728
Imagine a cardboard box exactly one foot on every side. Line the bottom with 1-inch sugar cubes: 12 rows of 12 is 144 cubes. Stack 12 layers of those and the box holds 12 × 144 = 1,728 cubes. So one cubic foot is always 1,728 cubic inches.
That also explains a common slip. A foot is 12 inches, but a cubic foot is not 12 cubic inches. It is 12 × 12 × 12.
Worked examples
- Calculator default: 24 × 12 × 6 in
- Cubic inches: 24 × 12 × 6 = 1,728 in³
- Cubic feet: 1,728 ÷ 1,728 = 1.0000 ft³
- Window box planter: 36 × 8 × 8 in inside
- Cubic inches: 36 × 8 × 8 = 2,304 in³
- Cubic feet: 2,304 ÷ 1,728 = 1.3333 ft³
A 1.5 ft³ bag of potting soil holds 1.5 × 1,728 = 2,592 in³. One bag fills this box with about 288 in³ left over, enough to top it up after the soil settles. The potting soil calculator does this for whole beds and containers.
Cubic inch conversion reference
| Unit | Cubic inches | Notes |
|---|---|---|
| 1 cubic centimeter (cc, mL) | 0.0610 | 1 in³ = 16.387 cc |
| 1 US liquid quart | 57.75 | |
| 1 liter | 61.02 | |
| 1 US gallon | 231 | Exact by definition |
| 1 cubic foot | 1,728 | 12 × 12 × 12 |
| 1 cubic yard | 46,656 | 36 × 36 × 36 |
| Box size (in) | Cubic inches | Cubic feet | US gallons |
|---|---|---|---|
| 12 × 12 × 12 | 1,728 | 1.0000 | 7.48 |
| 16 × 16 × 4 | 1,024 | 0.5926 | 4.43 |
| 18 × 10 × 8 | 1,440 | 0.8333 | 6.23 |
| 36 × 8 × 8 | 2,304 | 1.3333 | 9.97 |
Where cubic inches show up on a job
- Electrical boxes. Box fill is rated in cubic inches. A box stamped 18 in³ can hold only so many conductors, devices, and clamps.
- Engines and pumps. Displacement and pump chambers are often given in cubic inches or cc.
- Small concrete and grout pours. Filling a 4 × 4 × 36 in post sleeve takes 576 in³, which is one-third of a cubic foot.
- Shipping and storage. Box volume decides what fits on a shelf or in a carrier’s size limit.
How to measure for cubic inches
- Measure inside, not outside. A plastic tote with 1/4-inch walls loses half an inch in each direction. That can cut capacity by 5 to 10% on a small box.
- Use the fill height. For a planter or bin, measure to where the soil or contents will stop, not to the rim.
- Round to the nearest 1/8 inch, then convert. For a 10-3/8 inch side, enter 10.375.
- Tapered containers. For buckets and pots that narrow toward the bottom, average the top and bottom widths. The result is close enough for buying soil. For a true cone shape, use the cone volume calculator.
Common mistakes
- Mixing inches and feet. Entering 2 for a 2-ft side alongside other sides in inches gives an answer 12 times too small.
- Dividing by 12 instead of 1,728. Cubic inches ÷ 12 is not cubic feet. 1,728 in³ ÷ 12 = 144, which is the square inches in one square foot, not a volume.
- Using outside dimensions for shipping and inside for storage interchangeably. Carriers price on outside dimensions. What fits inside is smaller.
Related volume tools
Going bigger? The cubic feet calculator works in feet, and the cubic yard calculator handles bulk soil and gravel orders. For any box shape in feet, use the rectangular prism volume calculator.
Frequently asked questions
What's the formula for cubic inches?
Cubic inches = length × width × height, with all three measured in inches. A box 18 in long, 10 in wide, and 8 in tall holds 18 × 10 × 8 = 1,440 cubic inches.
How do I convert cubic inches to cubic feet?
Divide by 1,728. A cubic foot is a 12-inch cube, and 12 × 12 × 12 = 1,728 cubic inches. So 1,440 in³ is 1,440 ÷ 1,728 = 0.8333 ft³, and 2,592 in³ is exactly 1.5 ft³.
How many cubic inches are in a gallon?
A US liquid gallon is defined as exactly 231 cubic inches. Divide cubic inches by 231 to get gallons. A container of 1,728 in³ holds 7.48 gallons, which is why a cubic foot of water is about 7.48 gallons.
How do I convert cubic inches to liters or cc?
One cubic inch is 16.387 cubic centimeters (cc or mL), and one liter is about 61.02 cubic inches. A 350 cubic inch engine is 350 × 16.387 = 5,735 cc, or about 5.7 liters.
Why work in inches instead of feet?
Small items are measured in inches, and converting each side to feet first gives awkward decimals like 0.667 ft. Multiplying whole inches and dividing by 1,728 once at the end is quicker and less prone to rounding errors.
Estimates only. Verify quantities with your supplier before purchasing.