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

Burning a gallon of gas in a car generates about 20 pounds of carbon pollution.

From Slate • May 15, 2026

The retail-sales numbers reflect total dollars spent, so recorded sales grew rapidly in March as people spent more for each gallon of gasoline.

From The Wall Street Journal • May 14, 2026

When Erik Aarts, a senior fixed-income strategist at Touchstone Investments, recently filled up during a trip in California, he ended up paying more than $6.50 a gallon for gas.

From MarketWatch • May 14, 2026

The average price of a gallon of diesel in the United States is up around 50 percent since the start of the war, according to the AAA motor club.

From Barron's • May 13, 2026

Instead they’re scouring the house for empty gallon jugs to bring to the desalination machines.

From "Dry" by Neal Shusterman and Jarrod Shusterman