gallon

American  

[gal-uhn] / ˈgæl ən /

noun

1. a common unit of capacity in English-speaking countries, equal to four quarts, the U.S. standard gallon being equal to 231 cubic inches (3.7853 liters), and the British imperial gallon to 277.42 cubic inches (4.546 liters). gal.

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gallon British  

/ ˈɡælən /

noun

1. Also called: imperial gallon.  a unit of capacity equal to 277.42 cubic inches. 1 Brit gallon is equivalent to 1.20 US gallons or 4.55 litres

2. a unit of capacity equal to 231 cubic inches. 1 US gallon is equivalent to 0.83 imperial gallon or 3.79 litres

3. (plural) great quantities

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gallon Scientific  

/ găl′ən /

1. A unit of liquid volume or capacity in the US Customary System equal to 4 quarts (3.79 liters).

2. See Table at measurement

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Etymology

Origin of gallon

First recorded in 1250–1300; Middle English galo(u)n, gallon, from Old North French galon, derivative from base of Medieval Latin gallēta “jug, bucket,” of uncertain origin

Compare meaning

How does gallon compare to similar and commonly confused words? Explore the most common comparisons:

• gallon vs. liter
• pint vs. gallon

Explanation

The gallon is a unit of measurement used for liquids such as gasoline, water, and milk in the United States. If your car’s tank is running on empty, then you better pull over and buy at least a few more gallons of gas. A gallon is equivalent to 4 quarts of liquid or 3.785 liters. The United States is one of the last countries to use this term. Though the gallon has roots in the British Imperial Units measurement system, the United Kingdom and most countries around the world have switched to the newer International System of Units.

Example Sentences

De Haan said national average gasoline prices have risen 40 cents a gallon in the past week, to nearly $4.45 a gallon, while diesel is up to an average of $5.62 a gallon.

From Barron's • May 3, 2026

Gasoline prices in the U.S. were around $4.26 a gallon on average this week, as a MarketWatch report noted.

From MarketWatch • May 1, 2026

In Ohio, regular gasoline averaged $4.83 a gallon on Friday, according to AAA, which compared with $3.91 a week earlier, and $2.81 right before the Iran war began.

From The Wall Street Journal • May 1, 2026

At an average of $6.05 a gallon in California, it would cost almost $218 to fill up that same Ford F-150 truck.

From MarketWatch • May 1, 2026

A tin gallon can has been cut in half, the lip ragged and dangerous.

From "Catching Fire" by Suzanne Collins