Cubic Inches to Gallons Calculator
Enter a volume in cubic inches and instantly see the equivalent in US gallons, UK gallons, liters, quarts and fluid ounces.
in³
1 US gallon = 231 in³ exactly
- 1
Input volume (in³)
231 - 2
US gallon definition (÷ 231)
2311 US liquid gallon = 231 cubic inches exactly. - 3
US gallons = in³ ÷ 231
231 ÷ 231 = 1
How does this calculator work?
Divide cubic inches by 231 to get US gallons (exact by definition), by 277.419 for UK gallons, or by 61.0237 for liters. A 231 in³ volume is exactly 1 US gallon — the definition set by US law. For UK gallons, 1 imp gal = 4.54609 L ≈ 277.42 in³.
Formula
How this is calculated
The US liquid gallon is defined as exactly 231 cubic inches — a definition that dates to the British wine gallon standardised in 1707. Dividing any volume in cubic inches by 231 therefore gives the precise US gallon equivalent. This is an exact definition, not an approximation.
The UK imperial gallon is defined differently: 4.54609 liters, which converts to 277.419 in³. UK gallons are therefore larger than US gallons by about 20%. The liter is a metric unit; 1 liter = 1000 cm³ = 61.0237 in³, so dividing cubic inches by 61.0237 gives liters. US quarts (4 per gallon, 57.75 in³ each) and US fluid ounces (128 per gallon, 1.80469 in³ each) follow from the gallon definition.
This conversion is especially common when working with engine displacement (commonly measured in cubic inches in older US specifications), aquarium volumes, and hydraulic cylinder capacity. For example, a 350 in³ V8 engine displacement is 350 ÷ 231 ≈ 1.515 US gallons of swept volume.
Frequently asked questions
Exactly 231 cubic inches = 1 US liquid gallon. This is a defined value set by US law. The UK imperial gallon is larger at approximately 277.419 cubic inches.
Divide the cubic inches by 61.0237. For example, a 350 in³ engine = 350 ÷ 61.0237 ≈ 5.74 liters, often rounded to 5.7L.
Yes. Calculate the aquarium's volume in cubic inches (length × width × height in inches), then divide by 231 for US gallons or by 61.0237 for liters.
Also known as
TG we-Calculate Editorial Team. (2026). Cubic Inches to Gallons Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/cubic-inches-to-gallons-calculator
TG we-Calculate Editorial Team. "Cubic Inches to Gallons Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/cubic-inches-to-gallons-calculator.
TG we-Calculate Editorial Team, "Cubic Inches to Gallons Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/cubic-inches-to-gallons-calculator
@misc{wecalculate_cubic_inches_to_gallons_calculator, title = {Cubic Inches to Gallons Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/cubic-inches-to-gallons-calculator}}, year = {2026}, note = {TG we-Calculate} }
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