What This Calculator Does
This tool converts a volume measured in cubic inches (inĀ³) into US liquid gallons. By definition, one US liquid gallon equals exactly 231 cubic inches, so the conversion is a simple division. Note this uses the US gallon; the UK (imperial) gallon is different (about 277.42 inĀ³).
How to Use It
Enter the volume in cubic inches into the input box and the calculator instantly returns the equivalent number of US gallons. This is handy for engine displacement, tank sizing, aquariums, and any time you have a volume from a length Ć width Ć height measurement in inches.
The Formula Explained
The conversion uses:
$$\text{gallons} = \frac{\text{cubic inches}}{231}$$
The number 231 comes from the historical definition of the US gallon as 231 cubic inches. To go the other direction, multiply gallons by 231 to get cubic inches.
Worked Example
Suppose you have a tank with an internal volume of 2,310 cubic inches. Dividing by 231 gives $$2{,}310 \div 231 = 10 \text{ US gallons}.$$ A common engine displacement of 350 inĀ³ equals \(350 \div 231 \approx 1.515\) gallons.
FAQ
Is this US or UK gallons? This calculator outputs US liquid gallons (1 gal = 231 inĀ³). Imperial gallons are larger.
How many cubic inches are in a gallon? Exactly 231 cubic inches per US gallon.
How do I convert gallons back to cubic inches? Multiply the number of gallons by 231.
