Comparison of the Troy and the Avoirdupois weight (mass) sytems

• Abreviations: T = Troy; av = Avoirdupois; oz = ounce; lb = pound; g = gram
• 12 T oz = 1 T lb
• 16 av oz = 1 av lb
• T Oz = 31.104 g
• av Oz = 28.35 g
• 1 T lb = 373.24 g
• 1 av lb = 453.59 g

• 20 pennyweights = 1 T oz. Small amounts of Precious metals are sold by pennyweight.
• 480 grains = 1 T oz.

Troy oz is the same as an apothecary (pharmecutical) oz.