Convert troy grain to avoirdupois pound

The pound has been defined as 453.6 g since 1959, when the US, the UK and the Commonwealth agreed a common value; 16 ounces make a pound, and an ounce is 28.35 g. Body weight is given in pounds in the US and in stones and pounds in Britain, 14 lb to the stone. Do not confuse the ounce of weight with the fluid ounce, a volume, or with the troy ounce of precious metals, which is heavier.

Gold, silver and platinum are priced per troy ounce, 31.103 g, which is about 10 % heavier than the ordinary (avoirdupois) ounce of 28.35 g. Twelve troy ounces make a troy pound of 373 g, 20 pennyweights make an ounce, and the grain, 64.8 mg, is the one unit the two systems share; it also survives in the weights of bullets and, in the US, of old-fashioned medicine doses (5 grains of aspirin is 324 mg). A standard 400 oz 'good delivery' gold bar weighs 12.4 kg.