Both a gallon(gal) and a liter(L) are units of capacity.
A gallon is a unit in the US customary and the British imperial systems of measurement is used to measure very large volumes of liquids, while a liter is a metric unit of capacity, formerly defined as the volume of one kilogram of water under standard conditions.
Formula to convert gal to L.
To convert a gallon measurement to a liter measurement, multiply the volume by the conversion ratio which is 3.785.
This is due to the relationship that 1 gal is equivalent to 3.785 liters.
Volume in L = Volume in gal x 3.785
Convert 15 gallons to liters.
= 15 x 3.785
= 56.775 liters.