Pound (mass) has been defined as exactly . In the United Kingdom, the use of the international pound was implemented in the Weights and Measures Act 1963. An 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 . In the UK, the process of metrication and 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
Pound (mass) and for different applications, the pound (or its translation) has referred to broadly similar but not identical standards of mass or force. The libra (Latin for "scales / balance") is an ancient Roman unit of mass that was equivalent to approximately 328.9 grams. It was divided into 12 "unciae" (singular: "uncia"), or ounces. The "libra" is the origin of the abbreviation for pound, "lb". A number of different definitions of the pound have historically been used in Britain. Amongst these were the avoirdupois pound and the obsolete Tower, merchant's and London pounds. Troy pounds and ounces remain in use only