This converter turns cubic inches into US gallons instantly, using the exact factor 1 cubic inch = 0.004329004329 US gallons. Type any number and the result updates as you go — nothing is sent to a server, so the arithmetic happens entirely in your browser.
The volume of a one-inch cube, traditional for US engine displacement. Exactly 231 cubic inches — the US liquid gallon used for fuel and milk.
Because the relationship is a simple proportion, one multiplication does the whole job. The table further down gives pre-computed values for the amounts people look up most often, and the result panel also reports the reverse conversion so you can check the figure both ways.
The formula
cubic inches- The amount you are converting, measured in cubic inches
0.004329004329- The exact number of US gallons in one cubic inch
US gallons- The converted result
How it works, step by step
- Enter the number of cubic inches you want to convert.
- The value is multiplied by 0.004329004329, the exact conversion factor.
- The result is displayed in US gallons, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 cubic inches
Multiply 5 by 0.0043290043. That gives 0.021645 US gallons. A quick sanity check: one cubic inch is smaller than one US gallon, so the number should get smaller — and it does.
Converting 72 cubic inches
72 × 0.0043290043 = 0.311688 US gallons. Working backwards, 0.311688 ÷ 0.0043290043 returns 72 cubic inches, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many US gallons are in one cubic inch?
Exactly 0.004329004329. Every conversion on this page is that single number multiplied by your input, so the result carries no rounding error beyond what is shown.
What is the formula to convert cubic inches to US gallons?
Us Gallons = cubic inches × 0.004329004329. To reverse it, divide instead: cubic inches = US gallons ÷ 0.004329004329, which is the same as multiplying by 231.
Is the cubic inch bigger than the US gallon?
No. One cubic inch is only 0.004329 of a US gallon, so the US gallon is the larger unit.
Why does my answer differ slightly from other cubic-inches to us-gallons converters?
Most differences come from rounding the factor too early. This tool keeps full double precision through the calculation and only rounds at the final display step, and it also shows the unrounded value so you can see exactly where any difference appears.
What is a cubic inch?
The volume of a one-inch cube, traditional for US engine displacement.
What is a US gallon?
Exactly 231 cubic inches — the US liquid gallon used for fuel and milk.
Cubic Inches to US gallons reference table
| Cubic Inches | Us Gallons |
|---|---|
| 0.5 in³ | 0.002165 gal |
| 1 in³ | 0.004329 gal |
| 2 in³ | 0.008658 gal |
| 3 in³ | 0.012987 gal |
| 5 in³ | 0.021645 gal |
| 10 in³ | 0.04329 gal |
| 15 in³ | 0.064935 gal |
| 20 in³ | 0.08658 gal |
| 25 in³ | 0.108225 gal |
| 50 in³ | 0.21645 gal |
| 75 in³ | 0.324675 gal |
| 100 in³ | 0.4329 gal |
| 250 in³ | 1.0823 gal |
| 500 in³ | 2.1645 gal |
| 1000 in³ | 4.329 gal |
Exact factor: 1 cubic inch = 0.004329004329 US gallons. Values rounded for display.