Karat Purity Calculator (Grams) — 24K, 22K, 21K, 18K Pure Gold Content
A karat purity calculator converts the karat rating of a gold piece into the exact mass of pure gold (in grams) it contains. The karat scale runs 0-24, where 24 karat is theoretically 100% pure gold; in practice, "24K" jewellery is usually 99.9% (999 fine) or 99.99% (9999 fine). Lower karats are gold-alloy mixes — 22K is 91.67% pure, 21K is 87.5%, 18K is 75%, and 14K is 58.33%.
This tool takes a gross gram weight + karat value and returns: pure gold mass (g), alloy mass (g), purity percentage, and the equivalent money value at the live international XAU/USD spot rate converted to your local currency. It is the standard calculation used by gold buyers, scrap dealers, jewellers and pawn shops to value a piece by weight and purity.
How the calculation works
Pure gold (g) = Gross weight (g) × (Karat ÷ 24). For example, a 10 g ring at 22K contains 10 × (22 ÷ 24) = 9.167 g of pure gold. The remaining 0.833 g is the alloy metal (typically copper, silver or zinc, depending on the colour of the gold). Money value = pure gold mass × live XAU/USD spot price × your currency exchange rate.
Sample conversions
| Input | Result |
|---|---|
| 10 g of 24K gold | 10.000 g pure gold (999 fine, ~100%) |
| 10 g of 22K gold | 9.167 g pure gold (916 fine, 91.67%) |
| 10 g of 21K gold | 8.750 g pure gold (875 fine, 87.50%) |
| 10 g of 18K gold | 7.500 g pure gold (750 fine, 75.00%) |
| 10 g of 14K gold | 5.833 g pure gold (583 fine, 58.33%) |
When to use this calculator
- Scrap gold valuation — calculate the bullion-equivalent value of old jewellery before selling.
- Jewellery purchase verification — cross-check the hallmark stamp against the price quoted by the jeweller.
- Investment piece sizing — work out how many grams of pure gold you actually own across mixed-karat pieces.
- Pawn-loan estimation — most pawn shops lend a percentage of the pure-gold melt value, not the gross weight.
Frequently asked questions
Is 22K gold the same as 916 hallmark gold?
Yes. 22K gold is 22/24 pure = 91.67%, which is stamped as "916" (parts per 1000) on the hallmark. Indian and Pakistani jewellery is most commonly 22K (916). Saudi and UAE jewellery is often 21K (875) or 18K (750) for modern designs.
Why does my 10 g 22K ring not weigh exactly 9.167 g of pure gold after melting?
Refining loss accounts for ~0.5-1% mass shrinkage during melting, due to oxidation of the alloy metals and small particles lost to the crucible. A reputable refiner reports the post-refine mass; budget for ~1% slippage when valuing scrap.
How is 18K white gold different from 18K yellow gold for purity calculations?
Both are 75% pure gold by mass — only the alloy composition differs. Yellow 18K is alloyed with copper and silver; white 18K is alloyed with palladium, nickel or platinum. Purity is identical, so the karat calculator returns the same pure-gold mass.