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How many liters in a gallon?
A US gallon is 3.785 liters; a UK gallon is 4.546 liters. They're not the same — the imperial gallon is about 20% bigger.
3.785 LUS gallon
4.546 LUK gallon
20%difference
US vs UK gallon
| Measure | US | UK (imperial) |
|---|---|---|
| 1 gallon | 3.785 L | 4.546 L |
| Half gallon | 1.893 L | 2.273 L |
| 1 quart | 0.946 L | 1.137 L |
This trips people up constantly, especially for fuel economy: "40 mpg" means less in the US than the UK because the US gallon is smaller. Always check which gallon is meant.
Frequently asked questions
How many liters in a US gallon?
3.785 liters.
How many liters in a UK gallon?
4.546 liters — about 20% more than a US gallon.
Why are US and UK gallons different?
They come from different historical standards; the imperial gallon was redefined in 1824 based on water volume, the US kept an older wine-gallon measure.