What are litres and gallons?

A litre is the everyday metric unit of volume. It's defined as the space taken up by a cube measuring 10 centimetres on each side — one cubic decimetre — and it's the unit you'll see on every fuel pump, water bottle and paint tin in the UK. It isn't technically an SI base unit, but it's officially accepted for use alongside the metric system, which is why it's stayed the standard for liquid volume across Europe and most of the world.

A gallon is older and messier. It comes from British and American trading history, and — this is the part that trips most people up — there are two different gallons still in everyday use. The UK gallon (also called the imperial gallon) is the one used in Britain for fuel-economy figures, home-brewing recipes and older plumbing specs. The US gallon is smaller, and it's the one printed on American car manuals, US recipe sites and imported appliances. They share a name but not a size, which is exactly why a converter needs to ask which gallon you mean before it can give you a useful answer.

UK gallon vs US gallon: what's the difference?

The short version: a UK (imperial) gallon is 4.54609 litres, and a US gallon is 3.785411784 litres. That makes the UK gallon roughly 20% larger than its American counterpart — a gap big enough to genuinely throw off a recipe, a fuel estimate or a tank size if you use the wrong one.

The imperial gallon was formalised by the 1824 Weights and Measures Act as the volume of 10 pounds of distilled water at 62°F, and redefined in exact metric terms — 4.54609 litres, no water involved — by the 1985 Act. The US gallon took a different path: it's legally fixed at exactly 231 cubic inches, a figure that traces back to an old English wine-trade measure long before the imperial system existed. Because the two systems were standardised separately, on separate sides of the Atlantic, they never lined up.

In practice, this means:

• UK car handbooks, fuel-economy labels and MPG figures use the imperial gallon.
• US manuals, American recipes and most imported US appliances use the US gallon.
• Countries that historically followed the British imperial system (Ireland, Canada, and several Commonwealth nations) have largely switched to litres, but you'll still see the imperial gallon referenced in older documents.

If you're not sure which one a source means, "gallon" on its own is almost always the imperial gallon in a British context, and the US gallon everywhere else — but when accuracy matters, it's always worth checking both, which is exactly why the calculator above shows you either one at a tap.

The litres to gallons formula

Both conversions work the same way — divide your litres figure by the number of litres in one gallon of that type:

You never need to remember these — the calculator at the top of this page does the division for you to the decimal place, both ways, instantly. But it's worth knowing the formula if you ever need to sense-check a number by hand.

How to use this calculator

The tool above is built to answer a litres-to-gallons question in one glance, but it's got a few extra features worth knowing about so you get the most out of it:

1. Type a number into the Litres box. The UK gallons (or US gallons) result updates as you type — there's no "convert" button to press and nothing to submit.
2. Switch between UK gallon and US gallon. Use the toggle above the input to pick which gallon you want. The whole calculator — the number, the label, the colour theme and the jug on screen — updates immediately to match.
3. Flip the direction if you'd rather start from gallons. Tap the swap icon between the two boxes to turn it into a gallons-to-litres calculator instead, without losing your place.
4. Choose your decimal precision. Pick 2 decimals for a quick, rounded estimate, or 6 if you need scientific-grade precision for a formula or a lab measurement.
5. Jump to a common value with the quick-pick chips. 1 litre, 5 litres, a 20-litre jerry can, a 55-litre car tank, a 205-litre oil drum, or exactly 1 UK or US gallon — tap one to load it instantly.
6. Open the "All units" tab for the full picture. The same volume is broken down into 12 units at once — millilitres, cubic metres, UK and US quarts, pints and fluid ounces, and cubic feet and cubic inches — plus the exact formula used, worked out to 10 significant figures.
7. Watch the jugs. Two glass jugs — one calibrated to a UK gallon, one to a US gallon — fill in real time as you type, so you can actually see the ~20% size difference between the two standards rather than just read the number.
8. Revisit earlier conversions. Every value you enter is quietly saved to the History tab in your browser, so you can tap back to a figure you checked earlier without retyping it.
9. Copy a result in one tap. The copy button next to the litres or gallons box puts the exact figure straight onto your clipboard, ready to paste into an email, a spreadsheet or a shopping list.

What makes it different from a basic converter

Litres to gallons conversion table

A quick-reference chart for the values people look up most often — from a single litre up to a 1,000-litre bulk tank:

Need a value that isn't listed here? Type it straight into the calculator at the top of the page for an instant, exact answer at any number of decimal places.

UK vs US gallon: visual comparison

Litres to gallons for fuel tanks

UK filling stations have sold fuel by the litre since the 1980s, but fuel-economy figures on older cars, handbooks and road signs are still often quoted in miles per (imperial) gallon — which is exactly where a litres-to-gallons mix-up tends to happen. If your car's manual lists tank capacity in litres and you want to know it in gallons, here's roughly what to expect:

If you're importing a vehicle, buying parts from a US supplier, or just reading an American car forum, remember the manual almost certainly means the US gallon — a "16-gallon tank" in an American spec sheet is around 60.6 litres, not the ~72.7 litres it would be if it meant imperial gallons.

Common conversions people search for

A few figures come up again and again — here they are at a glance, both ways:

Frequently asked questions