I use the metric system and quote weight in grams as there is only one system of weight for the gram and this avoids confusion.
I do not sell my jewellery by weight. I quote the weight only to indicate approximately how heavy a piece is.
As there are 2 systems that use the ounce and the weight of these ounces differ, it is important to understand which system is being used for the weight.
Troy ounce (ozT)
Troy ounce (ozT) is the system of measurement used for gold and silver. The price of gold is quoted per troy oz. Not all weighing scales have the troy ounce as an option.
1ozT = 31.1035g
Avoirdupois ounce (oz)
The avoirdupois (av-er-du-poiz) system has been replaced in the UK by the metric system. It is still in use in the USA. It is the system of weight with the ounce, pound and stone used in the kitchen and bathroom scales. This system is still selectable on digital scales and should not be confused with the troy ounce.
1oz = 28.3495g