Convert gold purity between the karat and fineness systems. Enter a karat such as 18K or a fineness value such as 750 to see the equivalent karat, fineness, percentage purity and gold-to-alloy ratio.
Convert either direction using the 24-karat and 1,000-point scales.
These are mathematical conversions of the stated purity. They do not authenticate a physical gold item.
Karat and fineness describe the same underlying gold proportion using different scales. Karat divides the material into 24 parts, while fineness expresses gold content out of 1,000 parts.
This means a karat value can be converted directly to fineness without using a gold price or jewellery weight.
| Karat | Gold Percentage | Mathematical Fineness | Common Marking |
|---|---|---|---|
| 9K | 37.50% | 375 | 375 |
| 10K | 41.67% | 416.67 | 417 |
| 14K | 58.33% | 583.33 | 585 / 583 |
| 18K | 75.00% | 750 | 750 |
| 21K | 87.50% | 875 | 875 |
| 22K | 91.67% | 916.67 | 916 / 916.7 |
| 23K | 95.83% | 958.33 | 958 |
| 24K | 100% | 1000 | Fine gold products commonly marked 999 or 999.9 |
The mathematical 1,000-point equivalent of 24K is 1000. In commercial practice, fine gold is commonly specified with fineness markings such as 999 or 999.9 rather than a literal 1000 mark.
To convert karat to fineness, divide the karat value by 24 and multiply by 1,000.
Therefore, 18K gold is 750 fineness and contains 75% gold by the karat definition.
For 22K:
This is why 22K is commonly associated with 916 or 916.7 fineness.
To convert fineness to karat, divide the fineness by 1,000 and multiply by 24.
For 916.7 fineness:
The small difference from exactly 22K comes from rounding the fineness value to one decimal place.
A fineness number describes the proportion of gold in an alloy. It does not represent the price of the jewellery, coin or bullion.
For example, two pieces can both be 750 fineness while having very different weights, designs, workmanship charges, gemstone content and market prices.
Fineness and percentage are directly related. Divide fineness by 10 to obtain the percentage value.
Conversely, multiply a percentage by 10 to express it as fineness.
The traditional karat system treats pure gold as 24 parts out of 24. That mathematical relationship produces 1000 fineness.
However, commercial fine-gold products are normally described using a specified fineness such as 999 or 999.9 because manufactured gold may contain very small quantities of other elements and because fineness standards use defined tolerances.
Therefore, 24K and a specific 999 or 999.9 fineness mark should not be assumed to be literally identical specifications in every context.
A jewellery hallmark or fineness stamp can provide a useful stated purity value. For example, 750 is commonly associated with 18K gold, while 916 is commonly associated with 22K gold.
The converter can translate such a stated number into its equivalent mathematical karat value.
For a physical item of uncertain composition, however, a mathematical conversion does not replace professional testing or an assay.
This converter assumes the input represents the actual gold purity or fineness of the material. It does not test the metal.
Rounded hallmark values can produce slightly different mathematical karat results. This is normal and does not mean the conversion formula is incorrect.
For jewellery containing gemstones or other materials, purity describes the gold alloy rather than the total mass of the finished item.
Multiply karat by 1,000 and divide by 24. For example, 18K equals 750 fineness.
Multiply fineness by 24 and divide by 1,000. For example, 750 fineness equals 18K.
22K is mathematically 916.67 fineness and is commonly represented by markings such as 916 or 916.7.
18K equals 750 fineness, representing 75% gold.
14K is mathematically approximately 583.33 fineness, representing about 58.33% gold.
999 fineness means 999 parts per 1,000 are gold, equivalent to 99.9% gold.
They describe the same underlying proportion on different scales. Fineness uses parts per 1,000, while percentage uses parts per 100.
No. It only performs mathematical conversions of stated purity values and cannot determine whether a physical item is genuine.