Gallons to liters converter
Convertersconversion pair
Convert gallons to liters instantly: 1 US gallon is 3.785411784 liters. The exact inverse of liters-to-gallons, with a copy button and no pump math.
The US gallon is 3.785 liters — a milk jug with a hidden talent.
work surface
Math, not advice — results are indicative. Read the disclaimer.
pro tips
Quick mental math: multiply by 4. 5 gallons becomes about 20 liters, close enough for any brew.
1 gal ≈ 3.8 L — the milk jug conversion, memorized by every traveler.
5 gal ≈ 19 L: the homebrew batch and the aquarium favorite in one pair.
what it does
The gallons-to-liters trick runs backwards: multiply by 3.785411784 and the liters appear. It's the conversion you need the moment a gallon shows up somewhere that measures in liters — which is everywhere a milk jug shouldn't be.
You meet it on every US measurement abroad: the gas station where the pump reads gallons and the rental car wants liters, a homebrew recipe calling for five gallons (that's 19 liters of patient waiting), a fish tank "20 gallons" that actually holds 75.7 liters of water and opinions, or a paint can that insists on being a gallon everywhere.
The rough version: multiply by 4. Three gallons becomes about twelve liters, close enough for jugs, tanks and anything that doesn't get its own trophy. For everything else, the widget below is exact and never drips.
Type any gallon number and the widget answers in liters on the spot, with the math in the hint. Click the result to copy it, and hit swap when the conversation turns the other way — the liters-to-gallons version is waiting for it.
quick answers
How many liters are in a gallon?
Exactly 3.785411784 in a US gallon. For quick math use 3.8 — close enough for anything that doesn't float a boat.
How many liters are in 5 gallons?
18.9 liters. The homebrew batch, the gas can and the garage jug, all secretly the same size.
Is a UK gallon different from a US gallon?
Yes — the UK gallon is 4.546 liters, about 20% bigger. The US gallon won the convenience store; the UK one kept the tradition.
Why does the US still use gallons?
Early adoption and habit, same as miles. The gallon stayed in the US, and the liter just keeps being quietly right about the math.