GallonsTO LITRES
Convert between gallons and litres. Supports both UK imperial and US gallons — because a gallon isn't always a gallon.
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Volume Reference
Gallons to Litres
| Gallons | UK Litres | US Litres |
|---|---|---|
| 1 gal | 4.55 L | 3.79 L |
| 2 gal | 9.09 L | 7.57 L |
| 5 gal | 22.73 L | 18.93 L |
| 10 gal | 45.46 L | 37.85 L |
| 20 gal | 90.92 L | 75.71 L |
| 50 gal | 227.3 L | 189.27 L |
| 100 gal | 454.61 L | 378.54 L |
UK Fuel Context
Real-World Volumes
Typical car tank: 40 – 55 litres (about 9 – 12 UK gallons). A full tank at 145p/litre costs roughly £58 – £80.
Fuel economy: A car rated 50 mpg (UK) uses 5.65 L/100 km. Remember, UK mpg figures are ~20% higher than US mpg because the imperial gallon is larger.
Price per gallon: At 145p/litre, one UK gallon of petrol costs about £6.59. One US gallon at the same pump price would be £5.49.
Why you need a gallons-to-litres converter
The UK prices fuel in litres but measures fuel economy in miles per gallon. Car spec sheets quote tank capacity in litres, yet older drivers still think in gallons. If you are comparing fuel costs, planning a road trip, or just trying to make sense of your car's fuel gauge, you need to switch between the two constantly. This converter handles both UK imperial gallons and US gallons, because the two are not the same — a US gallon is about 20% smaller than a UK gallon, which catches people out when reading American car reviews or fuel economy figures.
How to convert gallons to litres
Multiply by the correct conversion factor for the gallon type you are using.
UK gallons to litres
Multiply by 4.54609. For example, 10 UK gallons = 10 x 4.54609 = 45.46 litres.
US gallons to litres
Multiply by 3.78541. For example, 10 US gallons = 10 x 3.78541 = 37.85 litres.
Litres to gallons
Divide the litre value by the appropriate factor. So 50 litres / 4.54609 = 11.0 UK gallons, or 50 / 3.78541 = 13.21 US gallons.
The conversion formulae
The imperial gallon was defined in 1824 as the volume of 10 pounds of water at 62 degrees Fahrenheit. The US gallon descends from the older English wine gallon of 231 cubic inches. Because they have different origins, they are different sizes. One imperial gallon is exactly 4.54609 litres, and one US gallon is exactly 3.785411784 litres. To convert UK mpg to L/100 km, divide 282.481 by the mpg figure.
Tips & Best Practices
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UK fuel economy is quoted in imperial mpg — do not compare directly with US mpg figures without converting
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For a rough estimate, a UK gallon is about 4.5 litres and a US gallon is about 3.8 litres
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A typical UK car tank holds 45-55 litres, which is roughly 10-12 imperial gallons
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When reading American car reviews, their mpg numbers will always look lower because US gallons are smaller
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To convert pence per litre to pounds per gallon (UK), multiply by 4.546 and divide by 100
Frequently Asked Questions
Mandeep Singh · 25+ Years UK Financial Services
Important Information
This calculator is for informational purposes only and does not constitute financial advice or a personal recommendation.
Results are estimates based on the information you provide and may not reflect your actual financial position.
You should consider seeking independent professional advice tailored to your specific circumstances before making any financial decision.