Convert Ounce (oz) to Pennyweight (pwt) instantly.
About these units
Ounce (oz)
The ounce is a unit equal to 1/16 of a pound, or approximately 28.3495 grams, with roots in ancient Roman "uncia"—one-twelfth of a pound. The ounce is used for measuring small masses in cooking, postal services, gemstones (troy ounces), and various consumer goods. Despite not being part of the metric system, the ounce remains a staple in US everyday life, from food packaging to hardware components. Its small size gives it a practical niche where grams might feel too unfamiliar for some audiences. Multiple ounce variants exist historically—avoirdupois, troy, apothecary—but the avoirdupois ounce is now the standard in general commerce. Its endurance reflects the cultural weight of imperial units and the long history of Western measurement systems.
Pennyweight (pwt)
The pennyweight, equal to 1/20 of a troy ounce or 1.55517384 grams, is a unit used primarily in the precious metals and jewelry industries. Its origins lie in medieval English coinage, when the weight of silver pennies provided a practical standard for small masses. Jewelers continue to use the pennyweight because many traditional pricing structures and metalworking conventions are built around troy-based subdivisions. For gold, silver, and dental alloys, the pennyweight remains easier to work with than grams due to long-established norms. Even though the metric system is now dominant scientifically, the pennyweight persists because industries tied to history—especially those involving money and precious goods—tend to maintain deeply rooted practices.