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

Gas prices at the pump nationally were back above $4 a gallon on average Wednesday, according to Patrick De Haan, head of petroleum analysis at GasBuddy.

From MarketWatch • Apr. 22, 2026

In Mexico, gas averaged $5.07 a gallon in March, of which nearly $2 was tax.

From The Wall Street Journal • Apr. 22, 2026

On the campaign trail, Hilton has pledged to slash taxes, make housing more affordable and bring the cost of gas down to $3 a gallon.

From Los Angeles Times • Apr. 22, 2026

Closer to home, U.S. jet-fuel prices hovered around $2.50 a gallon in late February and soared to nearly $5 a gallon earlier this month.

From MarketWatch • Apr. 22, 2026

Dan gave Brian a long-sleeved shirt and then threw up “what seemed a gallon of ash,” he remembered.

From "Mountain of Fire" by Rebecca E. F. Barone