Gallons (UK) : A gallon (UK) is a unit of volume, which is commonly used in the United Kingdom and semi-officially within Canada. It is defined as 4.54609 liters distinguished from the United States (liquid) gallon (≈ 3.79 L). Liters : The liter (also written "liter"; SI symbol L or l) is a non-SI metric system unit of volume. It is equal to 1 cubic decimeter (dm3), 1,000 cubic centimeters YepF.