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Ten Things You Maybe Didn't Know About the US Gallon

1. The US Gallon is exactly 231 cubic inches

That's not just a random number—it’s rooted in history and law. The US gallon is defined as 231 cubic inches, which equals about 3.785 litres. Precise and tidy.

2. It’s smaller than the UK (Imperial) Gallon

Even though both countries call it a “gallon,” the UK version is about 20% bigger. That’s why if you ever rent a car in Canada and fill up in gallons, you might be surprised by how far your tank seems to go.

3. It’s divided into 4 quarts, 8 pints, or 128 fluid ounces

The US customary system loves subdivisions. The gallon neatly splits down into smaller units, which is great for recipes, fuel, or measuring how much lemonade you can chug on a hot day.

4. It’s the standard unit for fuel volume in the US

If you've ever glanced at a gas pump in the States, you've seen gallons in action. It's how Americans think about gas mileage, too—miles per gallon (MPG) is a key stat for drivers.

5. The US liquid gallon differs from the US dry gallon

Yes, there’s a dry gallon too, mainly used for agriculture. It’s equal to about 4.4 litres—slightly larger than the liquid gallon—but it’s rarely seen in everyday use.

6. Gallons date back to medieval England

Originally used for wine and ale, the term “gallon” has roots in European trade. Over time, the US stuck with a version that evolved from the Queen Anne wine gallon of the early 1700s.

7. Milk and water are commonly sold by the gallon

Next time you’re in a US grocery store, take a stroll past the dairy section—you’ll see gallon jugs everywhere. It’s a standard size for big, bulky liquids.

8. It’s sometimes abbreviated as “gal.”

Especially in technical or industrial contexts, you’ll see “gal” as the shorthand. It’s not to be confused with “gal” as in a cool nickname for a woman, obviously.

9. There’s a mnemonic to remember the breakdown

Ever heard of “the gallon man”? It's a fun visual mnemonic used in schools where a big "G" (for gallon) contains 4 "Q"s (quarts), each holding 2 "P"s (pints), and so on. Super useful for kids—and adults who cook.

10. It plays a big role in American brewing and distilling

Many breweries, distilleries, and homebrew setups use the gallon as their go-to unit. So the next time you're enjoying a cold one, you might just be sipping on a product measured in gallons from start to finish.