Short answer: a UK gallon is 4.546 litres — a US gallon is 3.785 litres.
Full conversion tables and the UK vs US difference explained below.
Litres
Litres
When it comes to converting litres to gallons, it's important to understand which type of gallon you're working with. The UK Imperial gallon and the US liquid gallon are not the same — and that difference matters a great deal when calculating fuel costs and MPG figures.
| Litres | UK Gallons | US Gallons |
|---|---|---|
| 1 | 0.22 | 0.26 |
| 5 | 1.10 | 1.32 |
| 10 | 2.20 | 2.64 |
| 20 | 4.40 | 5.28 |
| 50 | 11.00 | 13.21 |
As you can see from the table above, the number of gallons is always smaller than the corresponding number of litres due to the difference in their sizes.
Most UK cars have fuel tanks between 45 and 70 litres. Here's how those translate to gallons:
| Tank Size (Litres) | UK Gallons | Typical Vehicle |
|---|---|---|
| 40L | 8.8 gal | Small city cars (e.g. Toyota Aygo) |
| 50L | 11.0 gal | Superminis (e.g. VW Polo, Renault Clio) |
| 55L | 12.1 gal | Family hatchbacks (e.g. VW Golf, Ford Focus) |
| 60L | 13.2 gal | Larger cars & SUVs (e.g. BMW 3 Series) |
| 70L | 15.4 gal | Large SUVs & estate cars |
The Imperial gallon is primarily used in the United Kingdom and other Commonwealth countries. It is defined as exactly 4.54609 litres. On the other side of the pond, the US gallon is commonly used in the United States and is slightly smaller than its Imperial counterpart, measuring around 3.78541 litres.
The difference dates back to the 19th century. The British Imperial system was standardised in 1824 based on the volume of 10 pounds of distilled water. The US continued using an older wine gallon measurement, which is why the two systems diverged. The result: a UK gallon is about 20% larger than a US gallon.
To convert litres to UK gallons, divide by 4.54609. To convert litres to US gallons, divide by 3.78541.
Going the other way — gallons to litres — simply multiply: UK gallons × 4.54609, or US gallons × 3.78541.
| Litres | UK gallons | US gallons |
|---|---|---|
| 1 L | 0.22 gal | 0.26 gal |
| 2 L | 0.44 gal | 0.53 gal |
| 5 L | 1.10 gal | 1.32 gal |
| 10 L | 2.20 gal | 2.64 gal |
| 15 L | 3.30 gal | 3.96 gal |
| 20 L | 4.40 gal | 5.28 gal |
| 25 L | 5.50 gal | 6.60 gal |
| 30 L | 6.60 gal | 7.93 gal |
| 35 L | 7.70 gal | 9.25 gal |
| 40 L | 8.80 gal | 10.57 gal |
| 45 L | 9.90 gal | 11.89 gal |
| 50 L | 11.00 gal | 13.21 gal |
| 55 L | 12.10 gal | 14.53 gal |
| 60 L | 13.20 gal | 15.85 gal |
| 70 L | 15.40 gal | 18.49 gal |
| 80 L | 17.60 gal | 21.13 gal |
| 100 L | 22.00 gal | 26.42 gal |
| 500 L | 109.98 gal | 132.09 gal |
| 1000 L | 219.97 gal | 264.17 gal |
Because the UK and US use different gallon sizes, a car's MPG figure means something different depending on which side of the Atlantic you're on. A car achieving 40 MPG (UK) is actually only getting around 33 MPG in US terms — the same amount of fuel, just measured against a smaller gallon. This is worth bearing in mind when comparing fuel economy figures from American car reviews or manufacturer specs. You can use our MPG calculator which supports both UK and US gallon measurements.