Liters to Gallons
Convert litres to gallons and back for both US and imperial gallons, which differ by about 20 per cent — a costly confusion if you miss it.
US gallons (3.785 L). The UK imperial gallon is 4.546 L — about 20% bigger.
| Liters | US gallons |
|---|---|
| 1 | 0.26 |
| 2 | 0.53 |
| 3 | 0.79 |
| 5 | 1.32 |
| 10 | 2.64 |
| 15 | 3.96 |
| 20 | 5.28 |
| 40 | 10.57 |
| 50 | 13.21 |
There are two gallons, and this page uses the American one
"Gallon" is not one unit. The US liquid gallon is defined as exactly 231 cubic inches, which comes to 3.785411784 litres. The Imperial gallon, used in the United Kingdom and much of the Commonwealth, is defined as exactly 4.54609 litres. They are not close.
This page converts to US gallons. That is not a guess — the conversion factor shipped here has a reciprocal of 3.785411784 litres, the US definition to the last digit. It is the right default for a general-audience tool, and worth saying out loud, because the word on the label is identical either way.
| System | One gallon | Defined as |
|---|---|---|
| US liquid | 3.785411784 L | 231 cubic inches exactly |
| Imperial | 4.54609 L | 4.54609 litres exactly |
An Imperial gallon is 20.1% bigger, so a number quoted without its system is a number that means two things:
| Litres | US gallons | Imperial gallons |
|---|---|---|
| 1 | 0.264 | 0.220 |
| 10 | 2.642 | 2.200 |
| 50 | 13.209 | 10.998 |
| 60 | 15.850 | 13.198 |
A 60-litre tank is 15.85 gallons in one country and 13.20 in the other. Fuel-economy figures quoted in miles per gallon carry the same fork, which is most of why British and American figures for the same car look so different.
And the fluid ounce goes the other way
Here is the part that catches everyone, including people who know about the two gallons. The Imperial gallon is bigger. The Imperial fluid ounce is smaller:
| System | Gallon | Ounces per gallon | One fluid ounce |
|---|---|---|---|
| US liquid | 3.785411784 L | 128 | 29.5735 mL |
| Imperial | 4.54609 L | 160 | 28.4131 mL |
The Imperial ounce is 3.9% smaller. The reason is division rather than measurement: a US gallon holds 128 ounces and an Imperial gallon holds 160. A larger vessel cut into more pieces gives smaller pieces. So any rule of the form "Imperial units are bigger" gets one of these two wrong.
Pints are where it bites hardest, because both systems use the word for an eighth of their own gallon:
| System | One pint | In its own ounces |
|---|---|---|
| US liquid | 473.18 mL | 16 |
| Imperial | 568.26 mL | 20 |
A pint in London is 20.1% larger than a pint in New York — necessarily the same percentage as the gallon gap, since both are an eighth. And "16 ounces" and "a pint" are the same thing in one system and not in the other, which is a genuine hazard in recipes rather than a curiosity.
The litre did not fork
Worth the contrast, because it shows the problem is not inherent to volume. A litre is exactly 1000 cubic centimetres by definition, the same number everywhere, and the metric ladder is powers of ten the whole way up:
| Unit | Cubic centimetres |
|---|---|
| millilitre | 1 |
| centilitre | 10 |
| litre | 1,000 |
| cubic metre | 1,000,000 |
Converting between metric volumes never raises the question of which system you meant. The fork is specific to the customary units, and specifically to two countries having standardised different historical gallons and kept the same word for both.
How to use
- Choose whether you mean US or imperial gallons.
- Type a value in either box.
- Read the converted figure instantly.
- Check which gallon a quoted figure uses before comparing prices or economy.
Frequently asked questions
How many litres in a gallon?
It depends which gallon. A US liquid gallon is exactly 3.785411784 litres. An imperial gallon, used in the UK and some Commonwealth countries, is exactly 4.54609 litres — about 20 per cent larger. Any figure quoted in gallons is ambiguous unless the system is stated.
Why are there two different gallons?
The US kept the older English wine gallon of 231 cubic inches after independence. Britain then redefined its gallon in 1824 as the volume of ten pounds of water, producing a larger unit. Neither side changed back, so the two have diverged ever since.
Does this affect fuel economy figures?
Substantially. A car rated at 40 miles per imperial gallon achieves only about 33 miles per US gallon, because the imperial gallon holds more fuel. Comparing a UK figure with a US one without converting overstates the UK car's efficiency by roughly a fifth.
What is a 55-gallon drum in litres?
About 208 litres if it is a US drum, which it usually is — the standard industrial drum is US-spec worldwide. The nominal European equivalent is a 200-litre drum, which is close but not identical, and the two are not interchangeable for shipping calculations.
How do I estimate in my head?
For US gallons, multiply litres by 0.26, or divide by 4 and add a little. For imperial, divide by 4.5. A 50-litre tank is about 13 US gallons or 11 imperial gallons.
Is a US dry gallon a third thing?
It is, though you will rarely meet it. The US dry gallon of about 4.405 litres survives in some agricultural measures, mostly for produce sold by the bushel and peck. For any liquid, the US liquid gallon is meant.
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