Sixteen avoirdupois ounces to the pound
The everyday (avoirdupois) pound is 16 ounces, and since 1959 it has been exactly 0.45359237 kg, which makes an ounce exactly 28.349523125 g. This is the ounce on kitchen scales, food labels and postage. Troy ounces used for gold and silver are a different unit — 31.1035 g, twelve to a troy pound — and fluid ounces measure volume, not weight; the ml to oz converter handles those.
Reading pounds and ounces
A decimal pound is sixteenths, not tenths: 2.5 lb is 2 lb 8 oz, 1.25 lb is 1 lb 4 oz and 0.1 lb is 1.6 oz. Baby weights, produce and parcels are quoted as pounds and ounces; the split row above does the arithmetic for you.