Gallons to Liters Calculator

The gallon is the primary unit for liquid volume in the United States — fuel tank capacities, water jugs, paint quantities, and pool volumes are all measured in gallons. The liter is the standard metric unit used everywhere else and is essential for international recipes, scientific work, and products sold globally. Converting between the two is a routine need for travelers checking fuel efficiency abroad, chefs scaling international recipes, engineers reviewing metric product specifications, and homeowners comparing liquid volumes across US and European packaging. One US liquid gallon is defined as exactly 3.785411784 liters. This calculator multiplies any gallon value by 3.78541 (the rounded constant) and returns the result to four decimal places, covering small beverage volumes up to large tank capacities.

Liters = Gallons × 3.78541. The conversion factor 3.78541 is derived from the legal definition of the US liquid gallon as exactly 231 cubic inches, combined with the metric definition of a liter as exactly one cubic decimeter (1,000 cubic centimeters). Working through those unit relationships gives 1 US gallon = 3.785411784 liters exactly. The calculator uses the rounded constant 3.78541, which introduces less than 0.00003% error — negligible for any practical purpose. The UK imperial gallon is a different unit (4.54609 liters) and is not used by this calculator. Results are displayed to four decimal places to provide precision for small volumes; large volumes like pool capacities will return large whole-number results.