BUYER'S GUIDE
Troy ounces, grams and gold fineness explained
Gold descriptions use grams, troy ounces and several ways of expressing fineness. Confusing one unit can undermine an entire price comparison. First establish whether the product description states the weight of the complete piece or its fine-gold content.
A troy ounce is a different unit
NIST conversion tables give exactly 31.1034768 g for one troy ounce. Gold descriptions may use oz t, t oz or simply oz in context. The ordinary avoirdupois ounce used for many everyday goods is approximately 28.35 g. It is not the correct unit for converting a gold coin's troy-ounce specification.
One tenth of a troy ounce is 3.11034768 g, often shown as approximately 3.11035 g for comparison. Round only at the end of your calculation. For several pieces, total the declared metal content first and then calculate the price per gram.
Understanding 999.9 fineness
Fineness expresses the proportion of gold in the material. The notations 999.9/1000 and 9999/10000 both represent 99.99%. A bare number such as 9999 should be read in the manufacturer's stated notation. Fineness does not describe a bar's size or identify its manufacturer.
For a hypothetical item with a gross weight of 10 g and a fineness of 900/1000, fine-gold content is 9 g. This illustrates the calculation, not an AURELIS product specification. If a specification already says ‘gold content 1 troy oz’, do not treat that fine content as the gross weight of an alloy and reduce it again.
Gemstone carats are a separate measurement
For gemstones, ct measures mass: one metric carat equals 0.2 g. Gold purity is also sometimes described using a carat or karat scale, such as 24-carat gold. Always include the material and unit in an enquiry: ‘2 ct tanzanite’ and ‘20 g gold bar, fineness …’ describe different attributes.
Compare declared metal content
Record the exact variant, unit, fineness and weight description. For PAX 2026, one 1 oz coin and ten 1/10 oz coins can be compared by gold content, but that does not imply identical prices or packaging. For bars, also verify the specification of the actual manufacturer supplied.
| Notation | Meaning |
|---|---|
| 1 oz t | 31.1034768 g |
| 1/10 oz t | 3.11034768 g |
| 999.9/1000 = 9999/10000 | 99.99% gold |
| 1 ct gemstone | 0.2 g; mass, not fineness |
Before sending an enquiry
- Does oz mean a troy ounce here?
- Is the weight gross or fine-metal content?
- Am I comparing the same units and rounding only at the end?
Sources and further reading
This guide helps compare products and order terms. It does not promise future returns or buyback.