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.
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.
The Karat System: Origin and Modern Use
The karat (from Greek kerátion, the carob seed used as a small weight in ancient Mediterranean trade) was adopted as a gold-purity scale in medieval Europe. A 24-karat standard was set because pure gold was considered to have 24 parts in 24 — an intrinsic fullness expressed in fractions. The scale is now codified in ISO 9202, which maps each karat to a fineness figure in parts-per-thousand: 24K → 999, 22K → 916, 21K → 875, 18K → 750, 14K → 585.
In South Asian jewellery markets, 22K (916 hallmark) is the dominant purity for bridal jewellery — hard enough to hold stone-set designs while remaining over 91% pure gold. Gulf jewellery (UAE, Saudi Arabia) typically runs 21K (875) for traditional pieces. European and US fine jewellery favours 18K (750) for colour latitude — white, rose and yellow gold each use different alloy compositions at the same 18K purity level.
For impurity content and refining yield at a given karat, the gold impurity calculator uses the same ratio to compute alloy mass. For conversions expressed in tola rather than grams, the karat purity calculator (Tola) keeps the output in South Asian units throughout.
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.
Step-by-step calculation
Example: 10 g of 22K gold
- 1
Find the karat ratio
ratio = karat ÷ 24
22 ÷ 24 = 0.9167
- 2
Calculate pure gold mass
pure (g) = gross × ratio
10 × 0.9167 = 9.167 g pure
- 3
Calculate alloy (impurity) mass
alloy (g) = gross − pure
10 − 9.167 = 0.833 g alloy
- 4
Calculate purity percentage
purity % = ratio × 100
0.9167 × 100 = 91.67% (916 fineness)
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%) |
Quick Reference — Karat Purity Scale
| Karat | Fineness |
|---|---|
| 24K | 999 |
| 22K | 916 |
| 21K | 875 |
| 18K | 750 |
| 14K | 585 |
| 10K | 417 |
| 9K | 375 |
ISO 9202 fineness values. 24K "fine gold" is 999.9 (four nines) in standard bullion.
Frequently asked questions
Is 22K gold the same as 916 hallmark gold?
Yes. 22K gold is 22/24 pure = 91.67%, stamped as "916" (parts per 1000) on the hallmark. South Asian bridal jewellery is most commonly 22K (916). Gulf jewellery is often 21K (875) and European or US fine jewellery favours 18K (750).
Why does my 10 g 22K ring not return exactly 9.167 g of pure gold after refining?
Refining loss (0.5–1%) accounts for oxidation of alloy metals and small particles lost to the crucible. A reputable refiner reports the post-refine mass. Budget for ~1% slippage when valuing scrap — the calculator shows the theoretical maximum, not the net-after-refine figure.
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 uses palladium, nickel or platinum. Purity is identical, so the karat calculator returns the same pure-gold mass regardless of colour.
What does "fineness" mean and how does it relate to karat?
Fineness is parts-per-thousand of pure gold: 916 = 91.6% = 22K; 750 = 75% = 18K; 999 = 99.9% = 24K. Most modern hallmark stamps show fineness rather than karat. To convert: fineness ÷ 10 = purity percentage; karat = fineness ÷ 41.67.
Can I calculate pure gold value without knowing the karat?
Not precisely. You need the karat stamp, a fineness hallmark, or an acid/XRF assay result. If a piece has no hallmark, most pawn shops and scrap dealers offer a free or low-cost acid test. Without a verified karat, any value figure is an estimate only.
Why is investment bullion 24K while most jewellery is 22K or lower?
Pure 24K gold is very soft and scratches under normal daily wear. Jewellery is alloyed down to 22K, 18K or 14K to improve hardness for wearable pieces. Bullion bars and coins are stored and handled rarely, so pure 24K maximises the gold content per gram without durability trade-offs.
How much pure gold do I get back when refining 22K jewellery to 24K bullion?
The theoretical yield is 91.67% of the gross 22K weight. After refining loss (0.5–1%), the practical net yield is ~90.5–91.1%. Most refiners also charge a fee (1–3%) on top of the process loss, so your effective return is typically 88–90% of the gross 22K weight in pure gold value.
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