For those accustomed to referring to liquid volume as pints, quarts and gallons, metric measurements of litres may pose a bit of a challenge. Converting the number of litres to gallons is further complicated by the fact that a U.S. gallon and the imperial gallon, used in the British Commonwealth, vary slightly. According to Nsx Prime, one imperial gallon equals 1.2009 U.S. gallons. The mathematical formula you use depends on whether you wish to convert litres to U.S. or imperial gallons.

Multiply the number of litres by .22 to convert to imperial gallons. For example, 10 litres multiplied by .22 equals 2.2 imperial gallons.

Multiply the number of litres by 0.26417 to convert to U.S. gallons. To convert 10 litres to U.S. gallons, multiple 10 by .26417 to get 2.6417 U.S. gallons.

Calculate a rough estimate of the number of gallons, when you already know the number of litres, by dividing by 4. Thus, 4 litres is approximately 1 gallon. A litre is approximately the same volume as a quart. For quick conversions in terms you are more familiar with, this will give you an approximate amount. For exact amounts, always use the above formulas.