gallon

American  

[gal-uhn] / ˈgæl ən /

noun

• gallons
  plural

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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Other Word Forms

Noun Inflected Forms

• gallons
  plural

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

See Examples For:

gallon gallons

Diesel topped $6 a gallon in September for the first time ever.

From MarketWatch ● Oct. 7, 2026

The average price of a gallon of diesel in California reached $8.35 this week, up more than 60% from a year ago, according to the American Automobile Assn.

From Los Angeles Times ● Oct. 7, 2026

Imported LNG costs about six times more than U.S. natural gas, while the price of heating oil in Massachusetts has increased to $6.12 a gallon from $3.53 a year ago.

From The Wall Street Journal ● Oct. 7, 2026

The president of the American Farm Bureau Federation says “every cent per gallon matters” when you run a fleet of grain trucks.

From MarketWatch ● Oct. 7, 2026

She poured a meager portion of Lucky Charms into a plastic bowl, and then she rummaged in the refrigerator for a gallon of milk.

From "Three Little Words: A Memoir" by Ashley Rhodes-Courter

The company claims it produced 19 million US gallons of water in the sky in three hours.

From BBC ● Oct. 7, 2026

For example, Rainmaker's 19 million gallons equates to around 0.01 inch of rain across 100 square miles.

From BBC ● Oct. 7, 2026

Transport loads are the cheapest way to buy dyed diesel, he said, with maybe 7,000 to 7,400 gallons per delivery.

From MarketWatch ● Oct. 6, 2026

Germany’s output fell nearly 6% to 79.2 million hectoliters, or about 2.1 billion gallons — a mark below 80 million hectoliters for the first time.

From Los Angeles Times ● Oct. 3, 2026

Yes, an untreated cholera patient may eventually die from producing diarrheal fluid at a rate of several gallons per day.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond