Convert gallons to liters instantly
Type in any number of gallons and this calculator shows you the exact liter equivalent right away. Whether you're adjusting a recipe, working out fuel economy, or checking a product label from another country, the answer is one click away.
1 US gallon = 3.78541 liters. That single fact powers every result this tool gives you.
How to use the gallons to liters calculator
- Enter the number of gallons in the input field above.
- The tool converts to liters automatically as you type — no button needed.
- Need to go the other way? Flip the units to convert liters to gallons instantly.
Worked example: 5 gallons to liters
Say you have a 5-gallon water jug and need to know how many liters that is for a metric measurement:
5 gallons × 3.78541 = 18.9271 litersSo 5 gallons ≈ 18.93 liters. Simple as that.
Another common one — filling a 15-gallon fish tank in metric:
15 gallons × 3.78541 = 56.7812 litersThat's roughly 56.8 liters.
How the conversion is calculated
The formula in plain words: multiply the number of gallons by 3.78541 to get liters.
liters = gallons × 3.78541The reverse is just as easy: divide liters by 3.78541 to get gallons.
gallons = liters ÷ 3.78541This factor comes from the official definition of the US liquid gallon, which equals exactly 231 cubic inches, which in turn equals 3.785411784 liters. The tool rounds to a practical number of decimal places.
Quick reference: gallons to liters table
| Gallons (US) | Liters |
|---|---|
| 1 | 3.785 |
| 2 | 7.571 |
| 5 | 18.927 |
| 10 | 37.854 |
| 25 | 94.635 |
| 50 | 189.271 |
| 100 | 378.541 |
Formula reminder: liters = gallons × 3.78541. To reverse it: gallons = liters ÷ 3.78541.
US gallons vs. UK (Imperial) gallons — which one are you using?
There are two types of gallon in common use, and they are not the same size. This matters if you're reading a British recipe or buying fuel in Canada.
- US liquid gallon = 3.78541 liters (most common for everyday use in the US)
- UK / Imperial gallon = 4.54609 liters (used in the UK, Ireland, and some Commonwealth countries)
This converter uses the US liquid gallon by default. If your source says "Imperial gallon" or you're working with UK measurements, multiply by 4.54609 instead.
When you'll use this conversion most
- Fuel and mileage: US gas pumps use gallons; most of the world measures fuel in liters. Useful when comparing MPG to L/100km.
- Cooking and brewing: American recipes often call for gallons or quarts; metric kitchens and homebrew guides use liters.
- Aquariums and pools: Tank sizes in gallons are common in the US; filtration systems and chemicals often list dosages in liters.
- Purchasing liquids abroad: Bottled water, paint, cleaning products — unit labeling differs by country.
Quick tips and things to watch out for
- Don't mix up US and Imperial gallons. A UK recipe calling for "1 gallon" is about 0.76 liters more than a US gallon — small in cooking, significant in fuel.
- Fluid ounces aren't just a small gallon. If you need to convert fluid ounces or quarts to liters, use those specific conversions rather than chaining through gallons.
- Rounding matters for precision work. For lab or industrial use, keep at least 5 decimal places (3.78541) rather than rounding to 3.8.
- Everything runs in your browser. No numbers are sent to a server — your inputs stay private on your own device.
Related ways people ask this question
People phrase this conversion in lots of ways — they all lead to the same math:
- How many liters in a gallon? → 3.785 liters per US gallon
- Gallon to litre (British spelling) → same result
- Liters per gallon → 3.78541 L/gal
- How many gallons in a liter? → 0.2642 gallons per liter
- Convert 2 gallons to liters → 7.571 liters
All of the above use the same factor; the tool handles each direction automatically when you swap units.
Bottom line: multiply your gallons by 3.78541 and you have liters. Use the calculator above to skip the math entirely.