Pennyweight (dwt)
The pennyweight is a troy unit of mass equal to 1/20 of a troy ounce or approximately 1.555 grams. Abbreviated as "dwt" (from the Latin denarius weight), it is used in the precious metals and jewellery industries for weighing gold, silver, and other fine metals, particularly in North American goldsmithing and dental gold applications.
Definition
One pennyweight equals exactly 1/20 of a troy ounce, 24 grains, approximately 1.55517 grams, or 1,555.17 milligrams. There are 20 pennyweights in a troy ounce. The pennyweight is part of the troy weight system and should not be confused with avoirdupois units.
History
The pennyweight derives its name from the weight of a medieval English silver penny. In the troy system, 20 pennyweights make one troy ounce and 240 pennyweights make one troy pound. The abbreviation "dwt" comes from the Latin denarius (penny) and the English "weight." While the troy ounce became the international standard for precious metals trading, the pennyweight remained in use among North American jewellers and goldsmiths as a finer subdivision.
Common Uses
North American jewellers weigh gold and silver in pennyweights when working with small quantities. Dental gold alloys are priced and sold by the pennyweight. Scrap gold buyers often quote prices per pennyweight. Jewellery appraisals in the US sometimes list gold weight in pennyweights. Outside North America, grams are used instead.
Did You Know? Facts About Pennyweight
- The abbreviation "dwt" comes from the Latin denarius (penny) + weight, not from any English abbreviation.
- A medieval English silver penny weighed exactly one pennyweight - 240 pennies made one troy pound of silver.
- 20 pennyweights make one troy ounce, and a pennyweight is about 1.56 grams.
- Dental gold is still commonly traded in pennyweights in the US.
- The British pre-decimal currency system (12 pence = 1 shilling, 20 shillings = 1 pound) mirrored the troy weight system (20 pennyweights = 1 ounce).