Free · Volume conversions

Cubic Inches to US Gallons Conversion Calculator

Convert cubic inches to us gallons with exact unit factors, editable results and an explained example.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

231 in³ = 1 US gal. The US liquid gallon contains exactly 231 cubic inches. It is smaller than the imperial gallon. Enter a known value in the units shown; editing a result solves the conversion in reverse.

231 in³ = 1 US gal

Worked example

Enter these known values and leave the other values blank.

Cubic inches
231 cu in
Gallons
1 US gal
Other volume units
3.7854 L

Assumptions and limitations

  • The US liquid gallon contains exactly 231 cubic inches. It is smaller than the imperial gallon.
  • The worked example uses the starting units. A unit selection preserves the quantity, so check the unit before entering a new number.
  • The optional oil-barrel unit uses 42 US liquid gallons. Dry gallons and dry quarts use the US dry-measure system and differ from liquid measures.
  • Where offered, a metric cup is 250 mL, a US legal cup is 240 mL, and the metric spoon choices are 5 mL and 15 mL. Fluid ounces measure volume rather than mass.

Common questions

Which volume convention does this conversion use?

The US liquid gallon contains exactly 231 cubic inches. It is smaller than the imperial gallon.

How should I use a rounded result?

Keep enough digits for the accuracy of the original measurement. Display rounding changes the visible precision, while the calculation retains additional digits.

References

Prices per thousand US gallons use the same exact gallon as the volume inputs. The option labeled oil barrel uses 42 US liquid gallons; the captured factor was approximately 31.5 gallons and did not match its oil-barrel label. The cubic international mile uses the cube of the exact 1609.344-meter mile, replacing a rounded reciprocal factor. The US customary cup uses one sixteenth of the exact US liquid gallon, replacing the rounded captured cup volume. The US fluid ounce uses one 128th of the exact US liquid gallon, replacing the rounded captured reciprocal factor. The US dry gallon uses one eighth of a 2150.42-cubic-inch bushel, replacing the rounded captured volume factor. Bookify replaces the captured rounded US gallon with the exact 3.785411784-liter definition.

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