Imperial units commonly used units for length are (li), (tseung/cheung), (tsek/chek), (tsun/chun), (fen/fan) in descending scale order. These units are now rarely used in daily life, the imperial and metric systems being preferred. The imperial equivalents are written with the same basic Chinese characters as the Chinese system. In order to distinguish between the units of the two systems, the units can be prefixed with "Ying" () for the Imperial system and "Wa" () for the Chinese system. In writing, derived characters are often used, with an additional (mouth) radical to the left of the original Chinese character, for writing imperial units.
Imperial and US customary measurement systems of any direction by Congress, the United States Treasury chose the second smallest gallon, the "Queen Anne gallon" of 231 cubic inches (3.785 litres) to be the official gallon in the United States for fiscal purposes. Sixteen US fluid ounces make a US pint (8 pints equals 1 gallon in both customary and imperial systems). During the reform of Weights and measures legislation in the United Kingdom in 1824, old gallons were replaced by the new imperial gallon which was defined to be the volume to 10 pounds of water at 62 °F (17 °C) and determined experimentally to be