Gallons to Liters Converter

The Gallons to Liters Converter turns any volume in gallons into liters — and, crucially, it does it for both the US gallon and the UK (Imperial) gallon at the same time. That matters because the word "gallon" is ambiguous: the same number of gallons is a different number of liters depending on which country's gallon you mean. This tool removes the guesswork, and it also runs in reverse to convert liters back to gallons.

How Many Liters Are in a Gallon?

There are exactly 3.785411784 liters in one US liquid gallon and exactly 4.54609 liters in one UK (Imperial) gallon. Both numbers are exact by definition, not rounded. Because the Imperial gallon is about 20% larger, the same gallon count always holds more liters if the gallons are UK gallons than if they are US gallons.

Gallons to Liters Formula

Converting gallons to liters is a single multiplication — you just pick the right factor for the gallon you have.

To go the other way, divide instead: US gallons = Liters ÷ 3.785411784, or UK gallons = Liters ÷ 4.54609.

US Gallon vs UK (Imperial) Gallon

A US liquid gallon is defined as exactly 3.785411784 liters (231 cubic inches). A UK or Imperial gallon is exactly 4.54609 liters. That makes the Imperial gallon roughly 20% larger than the US gallon. So if a recipe, fuel figure, or tank spec says "5 gallons," it means about 18.93 liters in the US but about 22.73 liters in the UK — a gap of nearly 4 liters. Always confirm which gallon your source uses.

Gallons to Liters Conversion Chart

Which Gallon Should I Use?

• Fuel in the United States: always the US gallon. American miles-per-gallon (MPG) figures use US gallons.
• Fuel in the UK and Ireland: sold in liters today, but older MPG figures and habits often still use the Imperial gallon, so UK MPG numbers look higher than US ones for the same car.
• Cooking and recipes: US recipes use US gallons, quarts, and cups; UK and Commonwealth recipes may use Imperial measures. Check the source country.
• Science and international trade: use liters (the SI unit) whenever possible to avoid confusion entirely.

Common Gallon Tank Sizes in Liters

• Motorcycle (~4 US gal): about 15 L (US) / 18 L (UK)
• Compact car (~12 US gal): about 45 L (US) / 55 L (UK)
• Mid-size SUV (~18 US gal): about 68 L (US) / 82 L (UK)
• Full-size pickup (~26 US gal): about 98 L (US) / 118 L (UK)
• Home aquarium (~55 US gal): about 208 L (US) / 250 L (UK)

How to Use This Calculator

1. Choose the direction: keep Gallons to Liters selected, or switch to Liters to Gallons for the reverse conversion.
2. Pick which gallon: choose US or UK (Imperial) so the highlighted answer matches your source — both are always shown.
3. Enter your volume: type the number of gallons, or click a fuel-tank preset to fill it in instantly.
4. Click Convert: the tool computes the result immediately.
5. Read both results: see the liters for a US and a UK gallon, watch the two tanks fill to those volumes, compare gallon sizes, and review the step-by-step formula.

Frequently Asked Questions

How many liters are in a gallon?

There are exactly 3.785411784 liters in one US liquid gallon and exactly 4.54609 liters in one UK (Imperial) gallon. To convert gallons to liters, multiply the number of gallons by the matching factor.

How do I convert gallons to liters?

Multiply the number of gallons by 3.785411784 for US gallons, or by 4.54609 for UK gallons. For example, 5 US gallons is 5 × 3.785411784 ≈ 18.93 liters, while 5 UK gallons is 5 × 4.54609 ≈ 22.73 liters.

Why does the same number of gallons give two different liter amounts?

Because the US and UK define the gallon differently. A US liquid gallon is 3.785411784 liters and a UK or Imperial gallon is 4.54609 liters, about 20 percent larger. So the same gallon number always holds more liters if the gallons are UK gallons than if they are US gallons.

How many liters is 5 gallons?

5 US gallons is about 18.93 liters and 5 UK (Imperial) gallons is about 22.73 liters. Multiply 5 by 3.785411784 for US gallons or by 4.54609 for UK gallons.

Which gallon is used for fuel?

The United States uses the US gallon for fuel and miles-per-gallon figures. The UK now sells fuel in liters, but older figures and some Commonwealth countries still reference the Imperial gallon, so always confirm which gallon a fuel figure uses before converting.

How many liters is a typical car fuel tank in gallons?

A compact car tank of about 12 US gallons is roughly 45 liters, a mid-size SUV of about 18 US gallons is roughly 68 liters, and a full-size pickup of about 26 US gallons is roughly 100 liters.

Additional Resources

• Gallon - Wikipedia
• Litre - Wikipedia