This converter turns US gallons into cubic inches instantly, using the exact factor 1 US gallon = 231 cubic inches. Type any number and the result updates as you go — nothing is sent to a server, so the arithmetic happens entirely in your browser.
Exactly 231 cubic inches — the US liquid gallon used for fuel and milk. The volume of a one-inch cube, traditional for US engine displacement.
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
US gallons- The amount you are converting, measured in US gallons
231- The exact number of cubic inches in one US gallon
cubic inches- The converted result
How it works, step by step
- Enter the number of US gallons you want to convert.
- The value is multiplied by 231, the exact conversion factor.
- The result is displayed in cubic inches, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 US gallons
Multiply 5 by 231. That gives 1,155 cubic inches. A quick sanity check: one US gallon is larger than one cubic inch, so the number should get bigger — and it does.
Converting 72 US gallons
72 × 231 = 16,632 cubic inches. Working backwards, 16,632 ÷ 231 returns 72 US gallons, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many cubic inches are in one US gallon?
Exactly 231. 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 US gallons to cubic inches?
Cubic Inches = US gallons × 231. To reverse it, divide instead: US gallons = cubic inches ÷ 231, which is the same as multiplying by 0.004329004329.
Is the US gallon bigger than the cubic inch?
Yes. One US gallon equals 231 cubic inches, so it is the larger unit.
Why does my answer differ slightly from other us-gallons to cubic-inches 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 US gallon?
Exactly 231 cubic inches — the US liquid gallon used for fuel and milk.
What is a cubic inch?
The volume of a one-inch cube, traditional for US engine displacement.
Us Gallons to cubic inches reference table
| Us Gallons | Cubic Inches |
|---|---|
| 0.5 gal | 115.5 in³ |
| 1 gal | 231 in³ |
| 2 gal | 462 in³ |
| 3 gal | 693 in³ |
| 5 gal | 1,155 in³ |
| 10 gal | 2,310 in³ |
| 15 gal | 3,465 in³ |
| 20 gal | 4,620 in³ |
| 25 gal | 5,775 in³ |
| 50 gal | 11,550 in³ |
| 75 gal | 17,325 in³ |
| 100 gal | 23,100 in³ |
| 250 gal | 57,750 in³ |
| 500 gal | 115,500 in³ |
| 1000 gal | 231,000 in³ |
Exact factor: 1 US gallon = 231 cubic inches. Values rounded for display.