A cubic inch is the volume of a one-inch cube.
Cubic inches to Gallons Converter — in3 to gal
Convert Cubic inch (in3) to Gallon (gal) using the exact conversion factor (1 cubic inch = 0.0043290043 gallon). See the formula, worked examples, conversion table, history, and common uses.
Cubic inches to Gallons converter
Converter
Volume Converter
Convert metric, US customary, imperial, cooking, dry, and industrial volume units.
Context values
Some unit families need one extra value for a physically accurate result.
A US liquid gallon is exactly 3.785411784 liters.
Result = input x 1.6387064e-5 / 0.003785411784.
Volume uses the cubic meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Cubic inches to Gallons
Cubic inch and Gallon appear side by side at fuel pumps and on beverage labels, since the US measures liquids in gallons while most of the world uses liters. Specifically: A cubic inch is the volume of a one-inch cube, and a US liquid gallon is exactly 3.785411784 liters.
Formula
gallons = cubic inches × 0.004329004329
This factor comes from each unit's defined relationship to the category's base unit: 1 cubic inch equals 0.000016387064 base units, and 1 gallon equals 0.003785411784 base units, so dividing one by the other gives the direct cubic inch-to-gallon factor of 0.004329004329.
Simple example
1 in3 × 0.004329004329 = 0.0043290043 gal
1 cubic inch = 0.0043290043 gallons.
Real-world example
10 in3 × 0.004329004329 = 0.0432900433 gal
10 cubic inches = 0.0432900433 gallons.
Conversion table
| Cubic inch (in3) | Gallon (gal) |
|---|---|
| 1 in3 | 0.0043290043 gal |
| 5 in3 | 0.0216450217 gal |
| 10 in3 | 0.0432900433 gal |
| 25 in3 | 0.1082251082 gal |
| 50 in3 | 0.2164502165 gal |
| 100 in3 | 0.4329004329 gal |
Reverse conversion: Gallon to Cubic inch
0.0043290043 gal × 231 = 0.9999999933 in3
0.0043290043 gallons = 0.9999999933 cubic inches.
cubic inches = gallons × 231
For a page dedicated to this direction, see Gallon to Cubic inch.
Understanding the Cubic inch (in3)
A cubic inch is the volume of a one-inch cube.
Understanding the Gallon
Gallon (gal) measures volume. The US liquid gallon is defined as exactly 231 cubic inches, equal to 3.785411784 liters. It is classified as a US customary unit.
Where it's used: United States (fuel, beverage, and liquid measurement)
US gallon vs. imperial gallon. The US liquid gallon (3.785411784 L) and the British imperial gallon (4.54609 L) are different units with the same name; always confirm which one a source is using.
Uses of the Gallon today
- Fuel pump and vehicle fuel-economy measurement in the US
- Beverage and liquid product packaging in the US
- Cooking and recipe measurement in US customary units
History of the Gallon
The US gallon descends from the English wine gallon of 231 cubic inches, a standard used for measuring wine in medieval and early modern England, which the American colonies inherited and retained even after England moved to a different imperial gallon in 1824.
England's 1824 Weights and Measures Act replaced the old wine gallon with a new imperial gallon (based on 10 pounds of water), but the US kept the older 231-cubic-inch definition — which is why the US gallon (3.785 L) and the imperial gallon (4.546 L) differ by about 20% today.
Historical origin. Gallon was not the invention of a single named person; it developed through the process described above.
Gallon — sources
- NIST Handbook 44, Appendix C — General tables of units of measurement, including the US gallon definition.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many gallons are in 1 cubic inch?
1 cubic inch equals 0.0043290043 gallons, using the exact defined conversion factor rather than an estimate.
How do I convert cubic inch to gallon?
Multiply the cubic inch value by 0.004329004329. The converter above does this instantly to whatever precision you set.
How do I convert gallon back to cubic inch?
Use the reverse factor: 1 gallon equals 231 cubic inches. You can also use the swap control in the converter above to flip the direction instantly.
What is a cubic inch?
Cubic inch (in3) is a unit of volume.
What is a gallon?
Gallon (gal) measures volume. The US liquid gallon is defined as exactly 231 cubic inches, equal to 3.785411784 liters. It is classified as a US customary unit.
Is the cubic inch to gallon conversion exact?
Yes. The US liquid gallon is defined as exactly 231 cubic inches, equal to 3.785411784 liters. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between us gallon vs. imperial gallon?
The US liquid gallon (3.785411784 L) and the British imperial gallon (4.54609 L) are different units with the same name; always confirm which one a source is using.