Precious Metal

The jewellery and bullion trades use units that look familiar but are not. A troy ounce, used for gold, silver and platinum, is about 31.10 grams, while the ordinary avoirdupois ounce used for groceries is about 28.35. Confusing them misprices a transaction by nearly ten percent, which on a single gold bar is a serious sum.

Gemstones bring their own vocabulary. Carat weight for a stone is exactly 0.2 grams, subdivided into one hundred points, so a fifty point diamond weighs half a carat. Confusingly, karat with a K describes gold purity rather than weight, where 24 karat is pure and 18 karat is seventy-five percent gold. The two words sound identical and mean entirely different things.

This converter handles troy ounces, grams, pennyweights, grains, carats and points so that valuations, insurance schedules and trade documents all use the same basis. Jewellers, collectors, pawnbrokers and private buyers can check a quoted weight rather than trusting an unstated unit.

How to use the Precious Metal

1. Identify the unit written on your certificate, invoice or scale.
2. Select that unit as the source in the converter.
3. Choose the unit you need for your records or comparison.
4. Enter the weight and read the converted value.
5. Record both figures with their units so no ambiguity survives in your paperwork.

Examples

• A collector converts a bullion coin quoted in troy ounces into grams to compare it with a local dealer's gram price.
• A jeweller converts a 0.75 carat stone into points for a valuation certificate.
• An insurer standardises a mixed inventory of gold and gemstone items into grams for a single schedule.

Frequently asked questions

What is the difference between a troy ounce and a normal ounce?

A troy ounce is approximately 31.103 grams and is used for precious metals. The avoirdupois ounce used for everyday goods is approximately 28.349 grams.

Is carat a measure of weight or purity?

Carat with a C is gemstone weight, fixed at 0.2 grams. Karat with a K is gold purity expressed in twenty-fourths.

What is a pennyweight?

A pennyweight is one twentieth of a troy ounce, roughly 1.555 grams. It is still common in North American jewellery workshops.

Does this tool price metals?

No. It converts weights only. Multiply the converted weight by a current spot price to estimate value.

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