The conversion factor
1 gallons (US) equals 3.78541 liters. Multiply your gallons (US) value by 3.78541 to get liters; divide to go back. For the reverse direction, use the liters to gallons (US) converter or the full volume converter.
Where this conversion comes up
Mixing metric and imperial is a daily reality in travel, shipping, recipes, fitness apps, and spec sheets — this page gives the exact factor plus a scannable table for the values people actually need.