Liters to Gallons: US vs Imperial, Explained
Convert liters to gallons using the exact US (3.78541 L) and UK imperial (4.54609 L) definitions. Table, examples, and why the two gallons differ by 20%.
The biggest trap in liters-to-gallons is picking the wrong gallon. The US gallon and the UK imperial gallon differ by nearly 20% — a huge gap that quietly changes fuel economy figures, brewing recipes, and cross-border price comparisons.
The formulas
US gallons = liters ÷ 3.78541 Imperial (UK) gallons = liters ÷ 4.54609
- 1 US gallon = 3.785411784 L exactly
- 1 imperial gallon = 4.54609 L exactly
*Example:* a car has a 50 L tank. 50 ÷ 3.78541 = 13.21 US gal 50 ÷ 4.54609 = 11.00 imperial gal
If you quote "13 gallons" without saying which, a UK driver will assume you mean 59 L. That's why fuel-economy comparisons between US mpg and UK mpg are meaningless unless you specify.
Reference table
| Liters | US gallons | UK imperial gallons |
|---|---|---|
| 1 L | 0.264 US gal | 0.220 imp gal |
| 5 L | 1.321 US gal | 1.100 imp gal |
| 10 L | 2.642 US gal | 2.200 imp gal |
| 20 L | 5.283 US gal | 4.399 imp gal |
| 50 L | 13.209 US gal | 10.998 imp gal |
| 100 L | 26.417 US gal | 21.997 imp gal |
| 200 L | 52.834 US gal | 43.994 imp gal |
For any custom volume, the Liters to Gallons converter supports both definitions.
The 20% gap — where it came from
Both gallons trace back to pre-metric English measures, but they descend from different traditions.
- The US gallon kept the older 1707 Queen Anne wine gallon: 231 cubic inches. That converts to 3.785 L. When the US and UK adopted the metric-anchored definitions in the 20th century, the US simply pegged its gallon to that older wine measure.
- The imperial gallon was newly defined by the UK's Weights and Measures Act 1824 as the volume of 10 pounds of water at 62 °F — about 4.546 L. It replaced a patchwork of older wine, ale, and corn gallons.
So the UK reformed and rounded up; the US kept the historical wine gallon. The ratio between them is 1 imp gal / 1 US gal ≈ 1.201.
The imperial gallon was itself dropped from UK legal trade in 1995, in favour of litres for fuel and packaging. It's still used informally for pub measures ("a pint") and in Ireland and some Commonwealth countries. Canada moved to litres for fuel in the 1970s but still occasionally quotes vehicle economy in "mpg (imperial)".
Fuel economy: the two-gallon problem
- US mpg — miles per US gallon. A US car listed at "30 mpg" burns 1 US gallon (3.785 L) per 30 miles.
- UK mpg — miles per imperial gallon. The same physical fuel economy shows as *36 mpg* on a UK spec sheet.
- L/100 km — the metric standard used by most of Europe. Lower is better.
So a "30 mpg (US)" car and a "36 mpg (UK)" car have identical fuel consumption. Any honest side-by-side comparison should convert both to L/100 km first — the Fuel Economy Calculator does exactly that.
Related everyday volume conversions live in our Ml to Fl Oz guide, which has the same US/UK split at smaller scale.
FAQ
Which gallon should I use? In the US, always "US gallons". In the UK, informally "imperial" but almost never on modern packaging (litres dominate). Elsewhere in the Commonwealth, check the source — Canada leans US, Australia and New Zealand leaned imperial before going fully metric.
How many liters in 1 gallon? US: 3.785 L. Imperial: 4.546 L. A useful mental shortcut: 1 US gal ≈ 3.8 L; 1 imp gal ≈ 4.5 L.
Why does a US pint look smaller than a UK pint? Because it *is*. A US pint is 473 mL; a UK pint is 568 mL — a full 20% larger. If you order a "pint" in a pub in London vs. New York, you'll get noticeably different amounts.
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*For an accurate conversion in either system, the free Liters to Gallons Converter supports both US and imperial gallons.*