What this calculator does
Turn liters into US gallons, or gallons into liters, in one step. Liters are how fuel, bottled water and engine oil are sold in most countries. Gallons are how Americans buy gasoline, milk and paint. You will need this when renting a car abroad, comparing fuel prices, or sizing an aquarium, water heater or rain barrel.
The US gallon is exactly 231 cubic inches. Since the inch is exactly 2.54 cm, that makes 1 US gallon exactly 3.785411784 liters. This page converts in either direction with that figure. The British imperial gallon is a separate, larger unit, covered in the pitfalls below.
Where it's used
Why this math matters outside the classroom:
- Fuel tanks. Travelers convert a 50 L fuel tank to about 13.2 US gallons.
- Water bottles. Campers packing water count a 1.5 L bottle as about 0.4 US gallons.
- Aquariums. A 200 L aquarium holds about 52.8 gallons.
- Paint cans. A paint can labeled 3.78 L holds one US gallon of 3.785 L, rounded on the label.
- Rain barrels. A 190 L rain barrel holds about 50 gallons.
Grade level and standards: Grades 5–6; Common Core State Standards for Mathematics 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter a volume in liters or in US gallons.
- Choose liters to gallons, or gallons to liters.
- Read the answer and working, and scan the table for typical amounts.
What the inputs mean
- Value to convert
- Liters for L → gal, or US liquid gallons for gal → L.
- Direction
- The direction of the conversion; the table switches to match.
Formula and method
L = US gal × 3.785411784 US gal = L ÷ 3.785411784 ≈ L × 0.264172052
In the formulas, L is the amount in liters and US gal is the amount in US gallons.
231 in³ (cubic inches) × (2.54 cm)³ = 3,785.411784 cm³ (cubic centimeters), which is 3.785411784 L. That means gallons to liters is exact.
Liters to gallons divides by that same number. Its flip side, 0.264172… (1 divided by it), goes on forever. So the calculator divides by the exact figure instead.
Worked example
A rental car's tank takes 50 L. How many US gallons is that?
- 1 US gal is exactly 3.785411784 L, so divide: 50 ÷ 3.785411784.
- 50 ÷ 3.785411784 = 13.2086026179…
Result: 50 L is about 13.21 US gallons.
Understanding the result
Mental shortcut: a gallon is a bit under 4 liters. For liters to gallons, divide by 4 and add 5%: 50 L → 12.5 + 0.6 ≈ 13.1 gal (exact 13.21). For gallons to liters, multiply by 3.8; the error is under 0.4%.
Examples: 15 US gal is 56.8 L and 20 US gal is 75.7 L. A 2 L soda bottle is just over half a gallon (0.53 gal). A gallon jug of milk holds 3.79 L.
Fuel prices: to compare a price per liter with a price per US gallon, multiply the per-liter price by 3.785. A fuel price of 1.50 per liter is about 5.68 per gallon in the same currency.
Assumptions and limitations
- “Gallon” means the US liquid gallon of 231 in³.
- Liters are SI liters, exactly 1 dm³.
- The imperial gallon (4.54609 L), still used in the UK for fuel economy figures, is not offered here; use the volume converter for it.
- The US dry gallon, a little-used grain measure, is not included.
Frequently asked questions
How many liters are in a gallon?
3.785411784 L in a US gallon, exactly. An imperial (UK) gallon is 4.54609 L.
Why is a UK gallon bigger?
The two countries standardized different historical gallons. Britain's 1824 imperial gallon was based on 10 pounds of water; the US kept an older 231-cubic-inch wine gallon. One imperial gallon is about 1.2 US gallons, which is why UK miles-per-gallon figures look higher.
How many gallons is 1 liter?
About 0.264 US gallons, or roughly a quarter gallon. A liter is slightly more than a US quart.
How much does a gallon of water weigh?
At room temperature, close to 3.78 kg, or about 8.3 lb, since a liter of water is close to 1 kg. The exact weight depends on temperature.
How this calculator is checked
Method: US liquid gallon = 231 in³ = 3.785411784 L exactly (from 1 in = 2.54 cm). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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