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

For many Americans, cutting back has already become the new reality after gas prices topped $4.50 a gallon for the first time in nearly four years.

From Los Angeles Times • May 23, 2026

California taxes consumers 70 cents per gallon of gas, the highest state tax in the country.

From Los Angeles Times • May 22, 2026

When drivers were filling up for Memorial Day last year, they were paying $3.18 per gallon.

From MarketWatch • May 19, 2026

The federal gas tax sits at 18.4 cents a gallon for gasoline and 24.4 cents a gallon for diesel.

From The Wall Street Journal • May 19, 2026

Uncle Darnell walked in with a gallon of cow’s milk from the McDaniels’ farm.

From "Gone Crazy in Alabama" by Rita Williams-Garcia