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Browse volume converters Gallons to liters

Gallons to Liters Converter

A tank marked “15 gallons” could hold about 56.8 or 68.2 liters. Enter a volume in gallons and choose whether the value uses US liquid gallons or Imperial gallons. The calculator converts the amount to liters using the selected gallon type.

US liquid gallons are selected by default. US and Imperial gallons are different sizes.

Automatic shows up to 9 decimals. Small nonzero values keep extra digits.

15 US liquid gal ≈ 56.78117676 L

Load a labeled quantity

Each example sets both the amount and gallon type. Sample capacities vary by product.

Confirm the gallon type before comparing capacities

Check the label, manual, or product specification for terms such as US gal, US liquid gallon, imp gal, or Imperial gallon. Do not rely only on the seller's country, because imported products and older manuals may use a different gallon standard.

An Imperial gallon is about 20.1% larger than a US liquid gallon, so choosing the wrong type can make a noticeable difference.

Same gallon count, different capacity. Liters are rounded to three decimals; the gap is calculated before rounding.
Label says US liquid (L) Imperial (L) Gap (L)
1 gal 3.785 4.546 0.761
5 gal 18.927 22.730 3.803
15 gal 56.781 68.191 11.410

Will a 20-liter container hold five gallons?

It depends on which gallon you mean. 5 US liquid gallons ≈ 18.93 L, so a 20 L container has about 1.07 L of space left. 5 Imperial gallons ≈ 22.73 L, which is about 2.73 L more than a 20 L container can hold.

Before filling a container, check whether its stated capacity is the usable volume or the maximum brimful volume. A label such as "5 gallon" does not always mean the container can safely hold the full converted amount in normal use.

Rated capacity and actual liquid volume are not the same

A container's stated capacity tells you how much it is designed to hold. It does not always tell you how much liquid is actually inside it.

Read a fuel receipt as the amount added

If a fuel receipt shows 12.4 US gal, that equals about 46.94 L. A car with a 15 US gal tank has a nominal capacity of about 56.78 L, but you should not use the difference between those two numbers to calculate exactly how much fuel was in the tank before filling. The tank rating is a stated capacity, while the receipt records the amount actually added.

For a receipt already in liters, convert liters to US gallons. Gallons-to-liters conversion alone does not convert an MPG fuel-economy figure to L/100 km.

Use the actual water amount for an aquarium

A 20 US gal aquarium ≈ 75.71 L by nominal capacity. The amount of water inside is usually lower because gravel, substrate, decorations, equipment, and space above the waterline take up part of the tank.

For a water change, convert the amount of water you actually remove or add rather than the aquarium's full rated capacity.

For smaller quantities, convert US gallons to US liquid quarts. If your measurement is in milliliters, convert milliliters to US gallons.

Two definitions; one multiplication

US liquid gallons
Liters = gallons × 3.785411784
Imperial gallons
Liters = gallons × 4.54609

Both conversion factors are exact. The US liquid gallon definition is listed in NIST Handbook 44, Appendix C while the imperial gallon factor is listed in NIST SP 811, Appendix B.8.

For most tank and container sizes, one or two decimal places are easy to read. Keep more digits when the result will be used in another calculation. Extra decimal places make the conversion more detailed, but they do not make the original measurement more accurate.

This calculator covers US liquid gallons and Imperial gallons. The US dry gallon is a different unit and is not included here. For other units, choose a unit in the volume hub. Converting a liquid volume to kilograms requires information about the liquid, such as its density.