Calculate gold purity in karat, percentage and fineness, or estimate the fine-gold content of a known jewellery weight. Use the preset karat grades or enter a custom purity value when you have a fineness or assay result.
Convert between karat, percentage and fineness.
Fine-gold content is shown only when a weight has been entered.
Gold purity describes how much of a gold alloy is actually gold. It is commonly expressed using karat, percentage or fineness.
Karat uses a 24-part scale. Percentage expresses gold content out of 100, while fineness expresses gold content out of 1,000.
| Karat | Approx. Gold % | Common Fineness |
|---|---|---|
| 24K | 100% | 999 / 999.9 commonly used commercially |
| 22K | 91.67% | 916.7 |
| 21K | 87.50% | 875 |
| 18K | 75.00% | 750 |
| 14K | 58.33% | 583.3 |
| 10K | 41.67% | 416.7 |
| 9K | 37.50% | 375 |
Commercial fineness markings can be stated using exact specifications such as 999, 999.9 or other standards, so the marking on a particular item should be used when available.
The karat system divides the alloy into 24 parts. The number of parts that are gold is the karat value.
For 18K gold:
For 22K gold:
The same relationship can be used for other karat grades.
Fineness expresses the gold content in parts per 1,000. A fineness of 750 means that 750 parts out of 1,000 are gold.
Fineness is especially useful for bullion and assay specifications because it can describe high-purity gold more precisely than a rounded karat grade.
Fineness can be converted back into karat using the 1,000-point scale.
For example, 750 fineness corresponds to:
A fineness of 916.7 corresponds closely to 22K, while 999 is approximately 24K in commercial purity terms.
A purity calculation becomes particularly useful when a gross jewellery weight is known.
Multiply the gross gold-alloy weight by the purity fraction to estimate the amount of fine gold represented by the alloy.
For example, 10 grams of 18K gold:
The remaining 2.5 grams represents the non-gold portion of the alloy.
Gross jewellery weight can include more than gold alloy. Rings, pendants and bracelets may contain gemstones, settings, enamel, solder or other materials.
Therefore, multiplying the total scale weight of a gemstone jewellery item by its karat fraction can overstate the actual fine-gold content if the non-gold components have not been separated or accounted for.
| Marking | Approx. Gold Content | Typical Karat Equivalent |
|---|---|---|
| 375 | 37.5% | 9K |
| 417 | 41.7% | 10K |
| 585 | 58.5% | ≈ 14K |
| 750 | 75.0% | 18K |
| 875 | 87.5% | 21K |
| 916 / 916.7 | ≈ 91.6–91.67% | 22K |
| 999 | 99.9% | ≈ 24K |
| 999.9 | 99.99% | Fine gold |
Hallmarking standards and marking practices vary by jurisdiction and product, so a stamp alone should not be treated as proof of authenticity.
Gold value calculations need more than gross weight. The amount of fine gold, current gold price and transaction terms can all affect the result.
Jewellery can also have making charges, gemstones, taxes, retailer margins and other components that are not captured by a simple fine-gold calculation.
This calculator focuses on purity and fine-gold content rather than providing a complete retail jewellery valuation.
No. A calculator can convert a stated karat, percentage or fineness value, but it cannot independently determine the composition of an unknown physical object.
For an unknown item, reliable purity determination may require appropriate professional testing or assay information. The calculator should be used to interpret a known or measured purity rather than as an authentication method.
This calculator assumes that the entered purity value correctly describes the gold material being evaluated.
A hallmark or stamp is useful information but does not by itself guarantee authenticity or actual composition.
For jewellery containing gemstones or other non-gold materials, the gross item weight should not automatically be used as the gold-alloy weight.
Divide the karat value by 24 and multiply by 100 for percentage purity. Divide the karat by 24 and multiply by 1,000 for fineness.
24K represents the highest karat grade. Commercial fine-gold products may be marked with fineness such as 999 or 999.9.
22K is 22/24 gold, approximately 91.67%, corresponding to about 916.7 fineness.
18K is 18/24 gold, equal to 75% or 750 fineness.
Multiply the gold-alloy weight by its purity fraction. Ten grams of 18K gold, for example, contains approximately 7.5 grams of fine gold.
No. Mathematical conversion cannot authenticate a physical item. Appropriate testing or assay information is needed for actual purity verification.
999 fineness means 999 parts per 1,000 are gold, equivalent to 99.9% gold.
916 fineness indicates approximately 916 parts per 1,000 are gold and is commonly associated with 22K gold.