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Gallon – Definition With Examples

Jessica Kaminski

reviewed by Maila Caliao

Updated on October 30, 2025

If you’re exploring the world of measurements, you might have come across the gallon. This unit of volume measurement is important to math and everyday life.

Here, Brighterly will cover the gallon meaning, history, uses, and conversions to other units of measurement. You can also try out our practice problems to hone your knowledge!

What is a gallon?

A gallon is a unit of volume measurement in the imperial system. The abbreviation of a gallon is gal. You’ll encounter this notion in daily life, as it’s used to measure common liquids like water, milk, and gasoline. Wondering how big is a gallon? It’s equivalent to 128 fluid ounces, 16 cups, 8 pints, or 4 quarts.

Gallon definition

The definition of a gallon is a unit of dry or liquid volume equivalent to 128 fluid ounces. Because it forms part of the US imperial system, it can be divided down into the smaller imperial measurements of quarts, pints, cups, and fluid ounces:

A gallon is equivalent to:

• 4 quarts
• 8 pints
• 16 cups
• 128 fluid ounces

History of gallon

The gallon measurement was first used to measure wine and ale in England during the Elizabethan era. Back then, the gallons for measuring wine and beer were smaller than the ale gallon. 

You may have also heard of the imperial gallon, a measurement occasionally used in England that is around 20% larger than the US gallon.

Uses of gallon

There are many uses for the gallon in our everyday lives. If you buy milk at the grocery store, it’ll be in a gallon size container. Gasoline is sold by the gallon in petrol stations, and you may have a water bottle measuring water in ounces, cups, and gallons!

How to convert gallon to liter?

To convert gallons to liters, you need to multiply your volume in gallons by 3.78541. For example, if you have 3 gallons, this would be 11.35623 liters:

3gal x 3.78541 = 11.35623.

If you’re wondering, “Is a gallon more than a liter?”, the answer is yes.

Liters to gallons formula

If you’re looking to convert from liters to gallons instead, the formula is liters ÷ 3.78541.

For example, 6 liters would be 1.585 gallons:

6l ÷ 3.78541 = 1.585

Gallon to liter table

When converting between a gallon and a liter, it can be helpful to have a handy reference like a table – so here it is!

Solved examples on a gallon

Here, we’ve created some solved math questions with explanations. So, you will better understand how to solve these types of problems.

Solved math task 1

How many liters are in 5 gallons of water?

Answer

5gal x 3.78541 = 18.92705 liters.

Solved math task 2

How many gallons are in 10 liters of milk?

Answer

10l ÷ 3.78541 = 2.64172.

Solved math task 3

You need 2 gallons of water for an experiment in science class, but your beaker only measures ounces. How many ounces will you need?

Answer

We know there are 128 fluid ounces in a gallon, so multiply that by 2 (your number of gallons).

128oz x 2 = 256.

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Practice problems on a gallon

Now, it’s time to try out some problems for yourself.

• You need to put 7 gallons of fuel in your car. How much is this in liters?
• You want to buy a fuel refill can and you see one with a 25-liter capacity. How much is this in gallons?
• You have a recipe that calls for 3 pints of milk. How much is this in gallons?

Conclusion

From this knowledge base, you’ve discovered what a gallon is, its history, and how you can convert it between different measurements. Knowing about the gallon measure isn’t just important for math – it’s key to your everyday life as you’ll encounter gallons of fuel, milk, water, and much more.

Frequently asked questions on gallon

How much is 1 gallon?

1 gallons is a unit of volume measurement that is equivalent to 128 fluid ounces, 16 cups, 8 pints, or 4 quarts. It is also equivalent to 3.78541 liters, if you’re familiar with the metric system.

What’s bigger than a gallon?

There are some measurements bigger than a gallon, including a barrel (31.5 gallons) and a hogshead (63 gallons). However, these aren’t commonly used measurements, so you’re likely to measure larger volumes in gallons, too.

Why are there different types of gallons?

There are two different gallon measurements, the US gallon and the imperial gallon, which arose from changes in how the US and UK measure volume over time.

What does a gallon of water look like?

A gallon of water will look like a large volume of water; if you’re more familiar with measurements like ounces, it will look like 128 ounces. That’s why gallons of water are often stored in jugs or large containers.

How do I convert gallons to liters and vice versa?

To convert gallons to liters, you need to multiply your volume in gallons by 3.78541.

For example, 4gal x 3.78541 = 15.14164.

To convert liters to gallons, divide your volume in liters by 3.78541.

For example, 9l ÷ 3.78541 = 2.37755.

Jessica Kaminski

81 articles

Jessica is a seasoned math tutor with over a decade of experience in the field. With a BSc and Master’s degree in Mathematics, she enjoys nurturing math geniuses, regardless of their age, grade, and skills. Apart from tutoring, Jessica blogs at Brighterly. She also has experience in child psychology, homeschooling and curriculum consultation for schools and EdTech websites.