Gallons to Liters
Enter a number of gallons, choose US or imperial, and see the liters at once. One US gallon is 3.785411784 liters and one imperial gallon is 4.54609 liters, so the answer depends on which gallon you mean. This page shows both results next to each other, plus milliliters, quarts, cups and fluid ounces.
Last updated November 4, 2026
Result
1 US gallon = 3.7854118 liters
| Unit | US gallons | Imperial gallons |
|---|---|---|
| Liters | 3.7854118 | 4.54609 |
| Milliliters | 3,785.4118 | 4,546.09 |
| US quarts | 4 | 4.8037997 |
| US cups | 16 | 19.215199 |
| US fluid ounces | 128 | 153.72159 |
1 US gal = 3.785411784 L, 1 imperial gal = 4.54609 L (both exact). Results are rounded to 8 significant digits.
Show the work
Formula: liters = gallons x liters per gallon (US 3.785411784, imperial 4.54609)
- Entered: 1 US gallon.
- Liters: 1 x 3.785411784 L per gallon = 3.7854118 L.
- Milliliters: 3.7854118 L x 1,000 = 3,785.4118 mL.
- US quarts: 3.7854118 L / 0.946352946 L per quart = 4.
- US cups: 3.7854118 L / 0.2365882365 L per cup = 16.
- US fluid ounces: 3.7854118 L / 0.0295735295625 L per fl oz = 128.
- Other gallon: 1 x 4.54609 = 4.54609 L, shown side by side.
Result: 1 US gallon = 3.7854118 liters
The gallons to liters formula
liters = US gallons × 3.785411784 · liters = imperial gallons × 4.54609
To change gallons into liters, multiply by the liters in one gallon. For US gallons the factor is exactly 3.785411784, because the US gallon is defined as 231 cubic inches. For imperial gallons the factor is exactly 4.54609, the figure fixed in United Kingdom weights and measures law. Neither factor is an approximation, so the only rounding comes from how many digits you display.
Milliliters are the liters times 1,000. The smaller US units come from dividing the liters by the liters in each unit: a US quart is 0.946352946 L, a US cup is 0.2365882365 L and a US fluid ounce is 0.0295735295625 L. The widget uses US quarts, cups and fluid ounces for both gallons, so you can compare the same volumes on one scale.
See how we calculate for the formulas, sources and review schedule behind every calculator.
Also useful alongside this calculator: Cups to Tablespoons Calculator, MPG Calculator and Length Converter.
Why the two gallons differ by about 20%
The imperial gallon is 4.54609 liters and the US gallon is 3.785411784 liters. Dividing one by the other shows that an imperial gallon is about 1.2009 US gallons, or about 20% more, and a US gallon is about 0.8327 imperial gallons. The gap is large enough to matter on any real quantity: 10 imperial gallons is 45.46 liters, while 10 US gallons is only 37.85 liters.
The US gallon comes from the old English wine gallon. The United Kingdom replaced its several gallons in 1824 with one imperial gallon, defined by the volume of ten pounds of water. The two units have been separate ever since. As a rule, US sources, American car manuals and US fuel prices mean the US gallon. The UK, and older material from Canada and some Commonwealth countries, may mean imperial.
When a figure does not say which one it is, check where it was written. If you cannot tell, convert both and see whether the difference changes your decision.
Tank size and fuel examples
A 15 US gallon fuel tank holds 56.78 liters. A car with a 15 imperial gallon tank holds 68.19 liters, about 11.4 liters more, so the label matters when you compare a UK car with a US one. A 50 US gallon water heater is about 189.27 liters, and a 10 US gallon aquarium about 37.85 liters.
For fuel economy, the same split applies. A car rated at 30 miles per US gallon travels 450 miles on a 15 US gallon tank. A rating of 30 miles per imperial gallon is about 36 miles per US gallon, because each imperial gallon is about 1.2 times larger. Put both figures in liters, or use the MPG calculator, before you compare cars from different countries.
Quarts, cups and fluid ounces in a gallon
One US gallon is 4 quarts, 8 pints, 16 cups or 128 fluid ounces, so a 5 US gallon bucket is 20 quarts, 80 cups or 640 fluid ounces. An imperial gallon is a bigger measure, so the same count of US units does not apply: it is about 4.8 US quarts, 19.2 US cups or 153.7 US fluid ounces. Imperial quarts and pints are also larger than the US ones, so do not read them as US units.
How to use the Gallons to Liters
- Enter the number of gallons as 0 or more; decimals such as 2.5 are fine.
- Choose US gallons or imperial gallons for the headline answer and the Show the work steps.
- Read the liters, milliliters, quarts, cups and fluid ounces for both gallons in the table.
- Use Copy, Print or Share to keep the result.
Worked example: a 15 gallon tank
Multiply 15 US gallons by 3.785411784 to get 56.78117676 liters, which is 60 quarts, 240 cups or 1,920 fluid ounces. For 15 imperial gallons, multiply by 4.54609 to get 68.19135 liters. The imperial tank holds 11.41 liters more.
| Gallons | US gallons in liters | Imperial gallons in liters | Imperial in US gallons |
|---|---|---|---|
| 1 | 3.7854 | 4.5461 | 1.201 |
| 5 | 18.9271 | 22.7305 | 6.005 |
| 10 | 37.8541 | 45.4609 | 12.009 |
| 15 | 56.7812 | 68.1913 | 18.014 |
| 20 | 75.7082 | 90.9218 | 24.019 |
Frequently asked questions
How many liters are in a gallon?
A US gallon is exactly 3.785411784 liters, and an imperial gallon is exactly 4.54609 liters. Use the US value unless the source is British.
Is a US gallon the same as an imperial gallon?
No. The imperial gallon is about 20% larger, roughly 1.2009 US gallons, so mixing them skews tank sizes, recipes and fuel economy by a fifth.
How many liters is a 15 gallon tank?
A 15 US gallon tank holds about 56.78 liters, while a 15 imperial gallon tank holds about 68.19 liters.
How do I convert liters back to gallons?
Divide the liters by 3.785411784 for US gallons, or by 4.54609 for imperial gallons. As a shortcut, one liter is about 0.2642 US gallons.
Which gallon do American recipes and gas stations use?
American recipes, gas pumps and product labels use the US gallon, which is 128 US fluid ounces or 16 US cups.