What Is pennyweight?
A pennyweight is a small unit of weight used mainly for gold, silver, and other precious metals. Jewelers and metal traders use it to measure and price fine metals accurately.
Definition
A pennyweight is a unit in the troy weight system, which is different from the regular weight system used for food or people.
- 1 pennyweight equals 24 grains.
- 1 pennyweight equals 1 divided by 20 of a troy ounce.
- 1 pennyweight is about 1.555 grams.
The troy system is common in the world of precious metals, so you will see pennyweight used together with troy ounces and grains.
History / Origin
The pennyweight comes from old English money and weight systems.
- Long ago, silver pennies were used as coins in England.
- The weight of these coins helped set the standard for small weight units.
- One penny coin was linked to what became known as a pennyweight.
Over time, coins changed, but the pennyweight stayed as a useful unit for goldsmiths, silversmiths, and jewelers. Today it remains part of the traditional troy weight system used for precious metals.
Symbol & Abbreviation
Pennyweight is usually shortened in these ways:
- dwt is the most common symbol for pennyweight.
- Sometimes you may see pwt, but this is less common.
In price lists or on jewelry scales, you will almost always see the unit written as dwt.
Current Use Around the World
The pennyweight is not used for everyday weighing like food or people. It is mostly used in special trades:
- Jewelry making Jewelers weigh gold, silver, and platinum in pennyweights to design and price rings, chains, and other items.
- Gold buying and selling Scrap gold buyers and refiners often quote weights and payments in pennyweights.
- Dental work Some dental alloys that contain precious metals may be measured in pennyweights.
Pennyweight is used in many countries that trade in gold and silver, especially where the troy system is known, like the United States, the United Kingdom, and Canada. However, grams and kilograms are more common in science and general trade.
Example Conversions
Here are some easy examples to show how pennyweight relates to other units.
Basic exact relationships
- 1 pennyweight dwt equals 24 grains.
- 1 troy ounce equals 20 pennyweights.
- 1 troy pound equals 12 troy ounces equals 240 pennyweights.
Conversions with decimals
- 1 pennyweight is about 1.555 grams.
- 1 pennyweight is about 0.05 troy ounces exactly 1 divided by 20.
- 1 gram is about 0.643 pennyweight.
- 1 troy ounce is about 31.103 grams which is 20 pennyweights.
Sample conversion table
| Pennyweight dwt | Grams g | Troy Ounces ozt | Grains gr |
|---|---|---|---|
| 1 dwt | ≈ 1.555 g | 0.05 ozt | 24 gr |
| 5 dwt | ≈ 7.78 g | 0.25 ozt | 120 gr |
| 10 dwt | ≈ 15.55 g | 0.5 ozt | 240 gr |
| 20 dwt | ≈ 31.10 g | 1 ozt | 480 gr |
Related Units
Pennyweight belongs to a family of units used for precious metals. These are closely related:
- Grain gr A very small unit. 24 grains equal 1 pennyweight.
- Troy ounce ozt A main unit in the troy system. 1 troy ounce equals 20 pennyweights.
- Troy pound A larger unit in the troy system. 1 troy pound equals 12 troy ounces or 240 pennyweights.
- Gram g The basic metric unit of mass. 1 pennyweight is about 1.555 grams.
- Carat ct Used for gemstones. 1 carat equals 0.2 grams. So 1 pennyweight is about 7.78 carats.
FAQs
Is a pennyweight the same as a regular ounce
No. A pennyweight is part of the troy system, not the regular avoirdupois system used for kitchen ounces. 1 pennyweight is 1 divided by 20 of a troy ounce, and a troy ounce is heavier than a regular ounce.
Why do jewelers use pennyweight
Jewelers use pennyweight because it fits well with the troy ounce system, which has been used for precious metals for a long time. It makes small amounts of gold and silver easy to measure and price.
How can I change pennyweight to grams
To convert pennyweight to grams, multiply the number of pennyweights by about 1.555. For example, 3 dwt times 1.555 is about 4.665 grams.
Is pennyweight still legal to use
In many places it is allowed for trade in precious metals, but for other goods, laws may require metric units like grams and kilograms or regular ounces and pounds. Jewelers and gold buyers often still use dwt daily.
What is the symbol for pennyweight on a scale
On a jewelry scale, pennyweight is usually shown as dwt. Some scales also let you switch between dwt, grams, and troy ounces.
Can I use pennyweight to weigh gemstones
You can, but it is not common. Gemstones are usually weighed in carats. Since 1 pennyweight is about 7.78 carats, it is easy to convert if needed.