Gold karat: what 10K, 14K, 18K and 24K mean
Karat is the measure of gold purity: how many parts in 24, by weight, are pure gold. 24K is pure gold, 18K is 18 parts gold to 6 parts other metals, and 14K is 14 parts gold in 24. Fineness, in parts per thousand, is the karat times 1000 divided by 24, so 18K is 750 and 14K is 583.
3D Jewelry Designer1 min read
Karat and fineness
The common karats work out like this:
| Karat | Fineness |
|---|---|
| 9K | 375 |
| 10K | 417 |
| 14K | 583 |
| 18K | 750 |
| 22K | 917 |
| 24K | 1000 |
Hallmarking standards use a short list of numbers, so a stamp can differ slightly from this arithmetic: 14K is commonly marked 585, and 22K 916.
Colour and weight
Karat fixes how much of the alloy is gold, and a lower-karat yellow gold is paler. The other metals set the colour, with more copper for rose gold and nickel or palladium for white, and change the density. Gold is denser than those metals, so the same ring weighs more at a higher karat: the alloy density table gives 13.07 grams per cubic centimetre for 14K yellow gold and 15.58 for 18K.
Karat and price
A gram of 18K holds 0.75 grams of pure gold, and a spot price is quoted for pure gold. Given the spot price per gram you enter, the ring cost estimator scales it by the alloy's fineness. In the ring builder, each karat and colour is a separate metal with its own density and, under cost-based pricing, its own price per gram.
Questions
Is karat the same as carat?
No. Karat is the purity of gold, while a carat is a unit of weight for gemstones, 0.2 grams. British English spells both carat and writes gold purity as ct, as in 18ct.
Related
- Hallmark and fineness: what 585, 750 and 925 mean
Fineness is the share of precious metal in an alloy, in parts per thousand. A hallmark states it on the piece: 585 on 14K gold, 750 on 18K, 925 on sterling.
- How much does an 18k gold ring weigh?
An 18K gold ring weighs its metal volume times the alloy's density. Grams per 100 mm³ for each 18K colour, and how to measure a ring's volume.
- Jewelry alloy density table: gold, platinum, silver
Density of every common jewellery casting alloy in grams per cubic centimetre, with the supplier table each figure comes from.