Imperial Gallon (imp gal)
The imperial gallon, shown as imp gal, is a British unit equal to 4.54609 liters. It came from English wine and drink measures in the 1800s and became official in 1824. The imperial gallon was used throughout the British Empire and is still used in the UK and some other countries for fuel and beverages. The liter is now used almost everywhere, but the imperial gallon still exists because of custom and local use.
US Gallon (gal)
The US gallon, denoted as gal, is a unit of volume that equals approximately 3.785 liters. It comes from old English wine gallons and became official in the US in the 1800s. People in the US still use it extensively for fuel, beverages, and cooking. The US gallon is smaller than the British one, which leads to different numbers in global trade and when comparing fuel use. Although most countries use metric units, the US gallon remains a significant part of US life.