How many litres are there in 1 Imperial gallon?

One Imperial gallon is equivalent to 4.54609 liters. When rounded to one decimal place, this is typically stated as approximately 4.5 liters. This measurement is based on the Imperial system, which is used in the United Kingdom and some other countries. The understanding of this conversion is significant, particularly in plumbing and related fields, where the accuracy of fluid measurements is essential for system designs and installations.

Thus, the answer of 4.5 liters is correct as it aligns with the standardized conversion from Imperial gallons to liters.