Gallons to liters converter

Multiply gallons by 3.78541 to get liters; divide liters by the same factor for gallons. The definition traces back to the US gallon being 231 cubic inches exactly, which the metric conversion of the inch turns into 3.785411784 liters.

The quick estimate is "call it three and three quarters": 5 gallons ≈ 19 liters (exactly 18.93), 10 gallons ≈ 38 liters (37.85). For fuel math, 1 liter is 0.264 gallons, and miles-per-gallon converts to liters-per-100-km by dividing 235.2 by the mpg figure.

The imperial gallon used historically in the UK, Canada, and Ireland is 4.54609 liters, 20% larger than the US gallon. A car achieving 40 mpg on imperial gallons is only managing 33 mpg on US ones, a discrepancy that has confused cross-border car shoppers for decades. All values on this page use the US gallon; if your source is British, multiply by 4.546 instead.

There is also the old US dry gallon (4.405 liters) for grain and produce, but it survives only inside the bushel, you will never meet it at a pump.

A typical US bathtub holds about 40 gallons (151 liters); a standard 10-gallon aquarium is 37.9 liters; the milk jug in American fridges is 1 gallon, 3.785 liters, while most of the world buys milk by the liter. Hydration challenges built around "a gallon a day" translate to 3.8 liters, roughly double the commonly cited adequate intake for women, which is worth knowing before you commit.