Quick answer: One UK (imperial) gallon is exactly 4.54609 litres, or about 4.55 litres for everyday use. To convert gallons to litres, multiply by 4.54609; to go back, multiply litres by 0.219969. A UK gallon holds 8 pints, which makes it roughly 20% larger than the 3.785-litre US gallon.
Fuel is sold by the litre, yet British drivers still talk in miles per gallon, and plenty of tanks, water butts and home-brew kits are described in gallons. The converter and charts below bridge the two systems. You will find related pints, litres and millilitres pages in our volume and capacity conversions hub.
UK gallons to litres
UK gallons= litresLitres to UK gallons
litres= UK gallonsHow many litres are in a UK gallon?
A UK gallon contains exactly 4.54609 litres. The value is written into Schedule 1 of the Weights and Measures Act 1985, which defines the gallon as 4.54609 cubic decimetres (one cubic decimetre being one litre). Because it is an exact legal definition, there is no rounding error hidden in the last digit.
The imperial gallon dates from the Weights and Measures Act 1824, when it was set as the volume of ten pounds of water under stated conditions. It was later fixed in terms of the litre so that it would no longer depend on weighing water. The gallon splits neatly into smaller imperial units: 4 quarts, 8 pints or 160 UK fluid ounces.
How do you convert UK gallons to litres?
Multiply the number of UK gallons by 4.54609 to get litres. For the reverse, divide litres by 4.54609, which is the same as multiplying by 0.219969. A rough mental shortcut is “gallons × 4.5”, which is accurate to within about 1%.
- Home-brew kit. Many beer kits make 23 litres. Divide 23 by 4.54609 and you get 5.06 UK gallons, which is why these kits are often sold as “5 gallon” or “40 pint” kits.
- Car fuel tank. A 55-litre tank holds 55 × 0.219969 = 12.10 UK gallons.
- Price per gallon. If fuel costs £1.40 a litre, one gallon costs 4.54609 × £1.40 = £6.36. This is a useful sum when you compare running costs quoted in miles per gallon.
Smaller quantities are easier in pints: our guide to how many ml are in a UK pint covers the 568 ml pint and its fractions.
UK gallons to litres chart
| UK gallons | Litres | UK pints |
|---|---|---|
| ½ gallon | 2.273 L | 4 |
| 1 gallon | 4.546 L | 8 |
| 2 gallons | 9.092 L | 16 |
| 3 gallons | 13.638 L | 24 |
| 5 gallons | 22.730 L | 40 |
| 10 gallons | 45.461 L | 80 |
| 12 gallons | 54.553 L | 96 |
| 15 gallons | 68.191 L | 120 |
| 20 gallons | 90.922 L | 160 |
| 50 gallons | 227.305 L | 400 |
| 100 gallons | 454.609 L | 800 |
How many UK gallons are in a litre?
One litre is 0.22 of a UK gallon. Put another way, it takes 4.55 litres to make a gallon, so ten litres is just 2.2 gallons. The table below covers common container sizes; for any other figure, try the litres to gallons converter.
| Litres | UK gallons | Typical example |
|---|---|---|
| 1 L | 0.220 | Carton of juice |
| 5 L | 1.100 | Screenwash or water bottle |
| 10 L | 2.200 | Bucket |
| 20 L | 4.399 | Jerrycan |
| 25 L | 5.499 | Large fermenting bin |
| 50 L | 10.998 | Small car fuel tank |
| 100 L | 21.997 | Small water butt |
| 200 L | 43.994 | Large water butt |
| 1,000 L | 219.969 | IBC tank (one cubic metre) |
Where is the gallon still used in the UK?
Mostly in miles per gallon, and in a few trades where older sizes stuck. Fuel has to be sold by the litre, but fuel economy is still widely quoted in mpg, and in UK sources the gallon in that figure is the 4.546-litre imperial gallon. You will also see gallons on cold-water storage cisterns, aquarium tanks, farm water troughs and home-brewing equipment, usually printed next to a litre figure.
How do you convert mpg to litres per 100 km?
Divide 282.48 by the UK mpg figure to get litres per 100 km. The constant comes from 100 × 4.54609 ÷ 1.609344, combining the imperial gallon with the exact length of a mile in kilometres (see the miles to km converter). Note that a lower L/100 km figure means a more economical car, the opposite of mpg.
| UK mpg | Litres per 100 km |
|---|---|
| 30 mpg | 9.42 |
| 40 mpg | 7.06 |
| 45 mpg | 6.28 |
| 50 mpg | 5.65 |
| 60 mpg | 4.71 |
| 70 mpg | 4.04 |
An mpg figure from an American website uses the smaller US gallon of 3.785 litres, so the same car will show a lower number there. Multiply US mpg by 1.201 to get UK mpg.
Frequently asked questions
Is a UK gallon 4.5 or 4.55 litres?
A UK gallon is exactly 4.54609 litres. Rounded to two decimal places that is 4.55 litres; 4.5 litres is a quick estimate that is about 1% too small.
How many litres is 5 UK gallons?
Five UK gallons is 22.73 litres. Multiply 5 by 4.54609 to get the exact figure of 22.73045 litres.
How many pints are in a UK gallon?
There are 8 pints in a UK gallon. Each imperial pint is 568.26 ml, and eight of them make 4.54609 litres.
Is a UK gallon bigger than a US gallon?
Yes. A UK gallon is 4.546 litres and a US gallon is 3.785 litres, so the imperial gallon is about 20% larger, a difference of roughly 0.76 litres.
Why is fuel sold in litres if cars use mpg?
UK law requires fuel to be sold in metric units, so pumps show litres. Miles per gallon survives as a familiar way of describing fuel economy, using the imperial gallon of 4.546 litres.
Sources
- Weights and Measures Act 1985, Schedule 1 (definitions of the gallon and pint), legislation.gov.uk
- NIST Guide to the SI, Appendix B.9 (UK and US gallon conversion factors)
- National Physical Laboratory (UK national measurement institute)
- Vehicle Certification Agency car fuel data (official UK fuel consumption figures)
More Volume and Capacity guides
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- How Many ml in a Teaspoon UK? 5 ml Explained
- Litres to Pints UK: Converter and Printable Chart
- UK Fluid Ounce vs US Fluid Ounce: What’s the Difference?
- Imperial Gallon vs US Gallon: The Difference Explained
- UK Gallon in Litres: Converter, Chart and mpg Guide