A US gallon is 3.785 litres and an imperial gallon is 4.546 litres. Type a number of gallons and the result appears straight away. The Gallon type switch under both fields picks one of three measures: US, UK and US dry.
A US liquid gallon is 3.785 litres. An imperial gallon, the one used in the UK, is 4.546 litres. The imperial gallon is 20% larger, so picking the wrong one costs you a fifth of the answer.
There is a third gallon as well: the US dry gallon, at 4.405 litres. It measures grain and produce sold by volume rather than by weight. You will meet it rarely, but neither of the other two can stand in for it, which is why the converter carries it under the US dry button.
If a source does not say which gallon it means, it is almost always the US liquid gallon. That is the measure behind fuel prices at American pumps, jerry cans, aquariums, water heaters and the oil barrel. The imperial gallon survives mainly in one place today: British fuel-economy figures, quoted as miles per gallon.
Until the eighteenth century England measured different goods with different gallons. Wine had one, ale had another, corn had a third, and each held a different volume. In 1707 the wine gallon was standardised at 231 cubic inches, which is exactly 3.785411784 litres. The American colonies adopted that measure and kept it after independence.
Britain took another road. The Weights and Measures Act of 1824 scrapped every older gallon and introduced a single imperial gallon, defined as the volume of ten pounds of distilled water, which works out at 4.54609 litres. The United States never adopted that reform.
That is the whole story behind the gap. Americans measure with the wine gallon of 1707, the British with the gallon of the 1824 reform, and both carry the same name.
The arithmetic itself is simple. For the US measure: litres = gallons × 3.7854. For the imperial one: litres = gallons × 4.5461. A jerry can sold as 5 gallons therefore holds 18.93 litres in the US and 22.73 litres in the UK.
The table sets the US and imperial gallon side by side, so the size of the gap is obvious at a glance. The US column matches the converter's default. For the dry gallon, read the value straight off the converter after selecting US dry.
| Gallons | US gallon | Imperial gallon |
|---|---|---|
| 0.5 gal | 1.89 l | 2.27 l |
| 1 gal | 3.79 l | 4.55 l |
| 2 gal | 7.57 l | 9.09 l |
| 3 gal | 11.36 l | 13.64 l |
| 4 gal | 15.14 l | 18.18 l |
| 5 gal | 18.93 l | 22.73 l |
| 10 gal | 37.85 l | 45.46 l |
| 15 gal | 56.78 l | 68.19 l |
| 20 gal | 75.71 l | 90.92 l |
| Gallons | US gallon | Imperial gallon |
|---|---|---|
| 25 gal | 94.64 l | 113.65 l |
| 30 gal | 113.56 l | 136.38 l |
| 40 gal | 151.42 l | 181.84 l |
| 42 gal | 158.99 l | 190.94 l |
| 50 gal | 189.27 l | 227.30 l |
| 55 gal | 208.20 l | 250.03 l |
| 100 gal | 378.54 l | 454.61 l |
| 275 gal | 1,040.99 l | 1,250.17 l |
Going the other way with a figure in litres? Head to the <a href="/en/tools/liters-to-gallons-converter">liters to gallons converter</a>, which also covers fuel prices per litre and metric fuel economy.
A handful of numbers come up so often in American listings that they have turned into product names. The table explains what sits behind each one, in the US measure.
| US gallons | Liters | What it is |
|---|---|---|
| 1 gal | 3.79 l | The standard milk jug in an American supermarket, and the daily amount behind the gallon-of-water challenge |
| 5 gal | 18.93 l | A fuel jerry can, a builder's bucket and the bottle on an office water cooler |
| 10 gal | 37.85 l | The smallest tank on a pet-shop aquarium shelf |
| 15 gal | 56.78 l | The fuel tank on a typical mid-size sedan |
| 26 gal | 98.42 l | The fuel tank on a full-size pickup |
| 40 gal | 151.42 l | A residential water heater |
| 42 gal | 158.99 l | A barrel of crude oil. It is a commodity-trading unit fixed in the nineteenth century, so it matches no drum in use today |
| 55 gal | 208.20 l | The steel industrial drum. Europe fills the same role with a 200-litre drum, which is 8 litres smaller |
| 275 gal | 1,040.99 l | An IBC tote, the plastic cube in a metal cage used to ship liquids. Europe sells it as a 1,000-litre unit, its working capacity |
European equivalents are rounded to whole hundreds of litres, which is why a 55-gallon drum and a 200-litre drum do the same job at slightly different capacities.
The switch under the fields has three options, and the situations below cover practically everything you will meet.
One US liquid gallon is 3.785411784 litres, or 3.79 litres rounded. The figure follows straight from the definition: a US gallon is 231 cubic inches.
One imperial gallon is 4.54609 litres, or 4.55 litres rounded. It is 20% larger than the US gallon.
Not quite, though it is a handy approximation. A US gallon falls 215 millilitres short of 4 litres, while an imperial gallon overshoots by 546 millilitres. Fine for one jerry can, but across a thousand-gallon tank the shortcut drifts by more than 200 litres.
Five US gallons are 18.93 litres and five imperial gallons are 22.73 litres. The US sum: 5 × 3.7854 = 18.93 litres. That is a fuel jerry can or a water-cooler bottle.
Ten US gallons are 37.85 litres and ten imperial gallons are 45.46 litres. That is the smallest aquarium size sold in American pet shops.
Half a US gallon is 1.89 litres and half an imperial gallon is 2.27 litres. Milk and juice in American shops are sold in exactly that half-gallon carton.
A barrel of crude is 42 US gallons, which is 158.99 litres. Pennsylvania oil producers settled on that size in the 1860s and commodity markets still quote it, even though nobody ships oil in barrels of that size any more.
A US gallon holds 128 US fluid ounces and an imperial gallon holds 160 imperial fluid ounces. The two numbers differ twice over, because the gallons differ and so do the ounces: a US fluid ounce is 29.57 millilitres against 28.41 for the imperial one. You can convert individual values in the <a class="inline-link" href="/en/tools/oz-to-ml-converter">oz to ml converter</a>.
A US gallon splits into 4 quarts, 8 pints and 16 cups. A US quart is 0.95 litres and a US pint is 0.47 litres. The imperial gallon divides into quarts and pints the same way, but an imperial pint holds 0.57 litres, because the whole gallon is larger. That is why a pint in a British pub is bigger than one in an American bar.
Size and ancestry. The US gallon is 3.7854 litres and descends from the English wine gallon standardised in 1707. The imperial gallon is 4.5461 litres and comes from the British measurement reform of 1824, which defined it as the volume of ten pounds of water. The gap reaches 20%, which on 55 gallons is almost 42 litres.
It is a third American measure, 4.40488 litres, used for goods sold by volume rather than weight, such as grain and berries. It descends from the old Winchester bushel and equals an eighth of one. It sits between the US liquid gallon and the imperial gallon, so neither of them substitutes for it. Pick it with the US dry button.
It means a US gallon, so 3.785 litres. Fitness guides and social media posts quote it as a gallon, while metric write-ups usually round it to 3.7 or 3.8 litres.
Multiply the gallons by 4. Twenty gallons gives 80 litres against an exact 75.71, so the shortcut runs about 5% high. Good enough to judge whether a tank fits, not good enough for an order.
No, it handles volume only. Fuel economy is a different quantity, because it ties volume to distance. The conversion table between litres per 100 km and miles per gallon, in both the US and the imperial scale, sits on the <a class="inline-link" href="/en/tools/liters-to-gallons-converter">liters to gallons converter</a> page.
If you have spotted an error in the tables or have an idea for improving the converter, drop us a line. We reply to every message.
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