Gallons to Litres Converter

Need to convert gallons to litres? This free online gallons to litres converter does it in your browser: type a value in gal and the L answer appears as you type, alongside the same figure in every other volume unit. Gallon (US) and Litre describe the same quantity on two different scales, so the gallons to litres conversion is a single arithmetic step once you know the exact factor. Nothing is uploaded and there is no sign-up — the answer is computed on your device as fast as you can type.

The gallons to litres formula

One gal is 3.7854 L:

L = gal × 3.7854
gal = L × 0.264172

That is the whole gallons to litres formula: multiply to go one way, divide — or multiply by the inverse — to come back. The factor is a defined constant rather than a measurement, so a gallons to litres conversion done this way carries no uncertainty of its own; the only open question is how many decimal places to display, which is covered further down.

Worked example

10 gal = 37.8541 L. Enter 10 in the box above and you will see exactly that, plus the value carried across the rest of the volume scale so you can sanity-check it against a unit you already recognise. It is the quickest way to convert gallons to litres when the answer has to be exact rather than estimated.

How to convert gallons to litres by hand

1. Write the value down in gal — 25 gal is used here.
2. Multiply it by 3.7854, because 1 gal = 3.7854 L.
3. Read the answer: 25 gal = 94.6353 L.
4. To come back, divide by 3.7854, or multiply by 0.264172 instead — 1 L = 0.264172 gal.

Gallons to Litres conversion table

Every figure below comes from the same engine as the box at the top of this page, shown at its Automatic precision, so each row is exactly what you would see after typing that value in. Treat it as a ready-made gallons to litres chart for the values people reach for most.

Why convert gallons to litres?

gallons to litres questions rarely arrive alone: they show up when metric jugs meet imperial recipes — cooking, fuel, drink sizes and lab measurements. In each case a gal reading has to become L — or be checked against one — before it can be used, and a guessed conversion is how the wrong size gets ordered, the wrong setting gets dialled in or the wrong amount gets poured. This free volume converter exists for that moment: the gallons to litres answer is exact, the full volume table sits one glance away, and everything runs locally in the browser — no sign-up, and none of the values you type are uploaded anywhere.

One gal in every volume unit

The 3.7854 L figure the converter shows for 1 gal is one row of this table — the row it defaults to. The others are here so a single reading can be checked against any further volume unit without running the conversion twice.

Estimating gallons to litres without a calculator

One habit worth keeping is to memorise two anchor points on the gallons-to-litres line: 10 gal is 37.8541 L, and 100 gal is 378.5412 L — both computed by the same engine as the converter above, not rounded by hand. With those anchors in mind, a mental gallons to litres estimate becomes a matter of proportion: a value between the anchors has an answer between them too, and a mental conversion that lands far outside them is a sign that the factor has almost certainly been inverted. The converter above is there for every time an estimate is not good enough.

Which direction the numbers move

Because 1 gal = 3.7854 L, converting gallons to litres increases the size of the number: 100 gal becomes 378.5412 L, while 100 L becomes 26.4172 gal. If a result moves the other way, the factor has been inverted — the two directions are reciprocals and never the same number.

How many decimals to keep

The relationship between gal and L is a defined constant, but written out in decimal it runs past eight places, so every figure on screen is a rounding of it. Automatic shows 3.7854, which is within 0.00031% of the true quotient, and the menu (Automatic, whole numbers, or 2, 4, 6 and 8 decimal places) keeps more or fewer digits when a specification asks for a fixed count.

gallons to litres in the real world

One US gallon is 3.78541 L because it is defined as 231 cubic inches — a number set in 1707 and never revised. The imperial gallon, defined in 1824 as the space taken by 10 lb of water, is 4.54609 L. The world's oil barrel remains 42 US gallons, 158.99 L, a size standardised by Pennsylvania oil coopers in the 1860s. Home brewing recipes travel badly here: a one-gallon kit is 4.5 L in a British extract tin but 3.8 L on an American one.

When people actually need gallons to litres

American appliances ship the question: a 40-gallon water heater holds 151 L, which is the number the UK or Australian plumber will ask for. The trap is national: a US gallon is 3.785 L and an imperial gallon 4.546 L, so a recipe, a fuel calculation or a sprayer mixing chart converted with the wrong gallon is off by a fifth of the whole volume.

About these units

Volume conversions have a wrinkle worth remembering: the US and UK gallons differ by about 20%. The figures here use the US customary definitions for cups, tablespoons, pints and gallons, and label the UK gallon separately.

Converting the other way

Press Swap to turn this into a L-to-gal converter in place. The inverse factor, 1 L = 0.264172 gal, is shown in the arithmetic panel so you can check the reverse calculation independently.

More volume converters

The same engine also powers Ml to Litres (1 mL = 0.001 L), Cups to Ml (1 cup = 236.5882 mL), Tbsp to Ml (1 tbsp = 14.7868 mL) and every other volume pair on this site, so the arithmetic is identical whichever two units you end up needing.