Gold Purity Calculator — Karat to Purity and Value
Calculate gold purity percentage and estimated value based on karat, weight, and current gold price per gram. This tool helps you determine the pure gold content in jewelry or bullion. See also our Percentage Calculator and Unit Price Calculator.
How to Calculate Gold Purity and Value
- Enter the weight of your gold item in grams.
- Select the karat rating (24K, 22K, 18K, 14K, or 10K).
- Enter the current gold price per gram (check live spot price).
- Click Calculate to see purity percentage, pure gold content, and estimated value.
- The value shown is the melt value of the pure gold content only.
Formula
Purity (%) = (Karat / 24) × 100
Pure Gold Weight = Total Weight × (Karat / 24)
Gold Value = Pure Gold Weight × Price per Gram
Example: 10g of 22K gold at $75/gram
Purity = (22 / 24) × 100 = 91.67%
Pure Gold = 10 × (22/24) = 9.167g
Value = 9.167 × $75 = $687.50Example
Suppose you have a 10-gram gold chain stamped 22K and the current gold price is $75 per gram. The purity of 22K gold is 22/24 = 91.67%. The pure gold content is 10 × 0.9167 = 9.167 grams. The remaining 0.833 grams is alloy metal (typically copper or silver). The melt value of the pure gold is 9.167 × $75 = $687.50. Note that retail jewelry value may be higher due to craftsmanship, brand, and design premiums.
Gold Karat Reference Table
| Karat | Purity (%) | Millesimal Fineness | Common Use |
|---|---|---|---|
| 24K | 99.9% | 999 | Investment bars, coins |
| 22K | 91.67% | 916 | Indian & Middle Eastern jewelry |
| 18K | 75.0% | 750 | Fine jewelry worldwide |
| 14K | 58.33% | 583 | US standard jewelry |
| 10K | 41.67% | 417 | Budget jewelry (US minimum) |
| 9K | 37.5% | 375 | UK minimum legal standard |
Frequently Asked Questions
What does karat mean in gold?
Karat (K or kt) measures gold purity on a scale of 1 to 24. Pure gold is 24 karat. 18K means 18 parts gold and 6 parts other metals out of 24 total parts, giving 75% purity.
What is the difference between karat and carat?
Karat (K) measures gold purity, while carat (ct) measures gemstone weight. One carat equals 0.2 grams. The terms are often confused but refer to completely different measurements.
Why is 24K gold not used for jewelry?
Pure 24K gold is too soft for everyday jewelry. It scratches and bends easily. Alloying with copper, silver, or zinc makes it harder and more durable while also allowing different colors (rose gold, white gold).
How do I find the current gold price?
Check financial websites for the live gold spot price, typically quoted per troy ounce. Divide by 31.1035 to get price per gram. As of 2024, gold trades around $65-80 per gram.
Is the calculated value what a jeweler will pay?
No. Jewelers typically pay 70-90% of melt value for scrap gold. They need margin for refining costs and profit. The calculated value represents the raw gold content value at spot price.