The United States and countries of the
Commonwealth of Nations agreed upon common definitions for the pound and the
yard. Since 1 July 1959, the
international avoirdupois pound (symbol lb) has been defined as exactly 59237 kg. 0.453
In the United Kingdom, the use of the international pound was implemented in the Weights and Measures Act 1963.
yard or the
metre shall be the unit of measurement of
length and the pound or the
kilogram shall be the unit of measurement of mass by reference to which any measurement involving a measurement of length or
mass shall be made in the United Kingdom; and- (a) the yard shall be 0.9144 metre exactly; (b) the pound shall be 0.45359237 kilogram exactly.
— Weights and Measures Act, 1963, Section 1(1)
avoirdupois pound is equal to 16 avoirdupois
ounces and to exactly 7,000
grains. The conversion factor between the kilogram and the international pound was therefore chosen to be divisible by 7, and an (international) grain is thus equal to exactly 91
In the UK, the process of
European units of measurement directives were expected to eliminate the use of the pound and ounce, but in 2007 the European Commission abandoned the requirement for metric-only labelling on packaged goods there, and allowed for dual metric–imperial marking to continue indefinitely.
 When used as a measurement of body weight the UK practice remains to use the
stone of 14 avoirdupois pounds as the primary measure e.g. "11 stone 4 pounds", rather than "158 pounds" (as done in the US),
 or "72 kilograms" as used elsewhere.
The US has not adopted the metric system
many efforts to do so, and the pound remains widely used as one of the key
United States customary units.