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Calculate how much alloy or pure gold to add to convert gold from one karat to another.
Gold & Silver
Generated on May 23, 2026
Adding material at 24K (100.00% pure). Auto mode picks pure gold when upgrading and pure alloy when downgrading.
Calculate how much alloy or pure gold to add to convert gold from one karat to another.
A karat adjustment calculator solves a practical jewellery-workshop problem: you have X weight of Y-karat gold, and you want to end up with Z-karat gold — how much metal do you need to add, and what type? If you're downgrading karat (e.
Formula
Weight to add = Current Weight × (K_target − K_current) ÷ (K_added − K_target).Your daughter's wedding is six months out, you're sitting in your favourite Sarafa Bazar shop, and you've just brought in 10 tola of 24K pure gold (inherited from your mother) that you want recast as 22K wedding jewellery — softer than 24K, harder than nothing, the standard for Pakistani bridal sets. The karigar nods knowingly and says he'll need to "add a little alloy." How much exactly? This calculator solves that practical workshop problem: you have X weight of Y-karat gold, you want to end up with Z-karat — how much metal to add, and what type? Downgrading karat (24K → 22K for durability) means adding pure alloy. Upgrading (18K → 22K for higher gold content) means adding pure 24K gold. The math handles both directions automatically. Working jewellers use this formula daily; this just puts it on your phone so you can verify what your karigar tells you. Honest take: upgrading old low-karat to high karat is almost never economical — you're essentially buying new gold AND paying labour, when you could just sell the old at melt value and buy new outright. Downgrading is more common and more sensible: it's how families inherited 24K pure-bullion-style jewellery from one generation get converted into modern 22K wearable pieces for the next generation. Know the math, verify the addition, and you walk out with what you actually paid for.
A karat adjustment calculator solves a practical jewellery-workshop problem: you have X weight of Y-karat gold, and you want to end up with Z-karat gold — how much metal do you need to add, and what type? If you're downgrading karat (e.g., 24K → 22K to make jewellery more durable), you add pure alloy. If you're upgrading (e.g., 18K → 22K for higher purity), you add pure 24K gold. The calculator handles both directions automatically, shows the exact amount to add in all units, and verifies the resulting purity. It's used by working jewellers, goldsmith apprentices, and anyone melting down old jewellery to recast at a different karat.
This generalized formula handles both downgrading (adding alloy) and upgrading (adding pure gold). When downgrading, K_target < K_current and you typically add 0K alloy, so the denominator becomes negative, the numerator is negative, and the quotient is positive — the amount of alloy to add. When upgrading, K_target > K_current and you add 24K gold; both numerator and denominator are positive. The calculator auto-selects 24K or 0K based on direction, but also supports a custom karat in case you're combining gold of a specific intermediate karat (e.g., melting 22K old stock into 18K new).
How much pure 24K gold is contained in 100 g of any karat — useful for planning jewellery upgrades/downgrades.
| Starting Karat | Pure 24K in 100 g | To Convert to 24K, Add | To Convert to 22K, Add/Remove |
|---|---|---|---|
| 24K → 22K | 100 g | — | Add 9.09 g of alloy |
| 22K → 24K | 91.67 g | Add 100 g of 24K + remove alloy | — |
| 22K → 18K | 91.67 g | — | Add 22.22 g of alloy |
| 18K → 22K | 75.00 g | — | Add 22.22 g of pure 24K |
| 18K → 24K | 75.00 g | Add 300 g of 24K + remove alloy | Add 22.22 g of pure gold |
| 14K → 22K | 58.33 g | — | Add 57.14 g of pure gold |
| 14K → 18K | 58.33 g | — | Add 33.33 g of pure gold |
Upgrading 100 g of 22K to 24K requires physically melting the piece — it's not a simple 'add pure gold' operation.
Downgrading 22K to 18K is common when re-crafting inherited jewellery with weight-to-value priorities.
Most Pakistani jewellers accept old jewellery as partial payment for new pieces at the 24K-equivalent rate.
Melting charges typically run 3–8% of metal value — always factor this into karat-adjustment planning.
Have 10 tola of 24K pure gold, want to convert to 22K: alloy to add = 10 × (22 − 24)/(0 − 22) = 0.909 tola of alloy; new total 10.909 tola of 22K.
Have 10 tola of 18K, want to convert to 22K: pure 24K to add = 10 × (22 − 18)/(24 − 22) = 20 tola of pure gold; new total 30 tola of 22K.
Have 50 g of 22K, want 21K (Middle Eastern grade): alloy to add = 50 × (21 − 22)/(0 − 21) = 2.38 g alloy; new total 52.38 g.
Have 100 g of 14K, want to upgrade to 18K for resale: 24K to add = 100 × (18 − 14)/(24 − 18) = 66.67 g pure gold; new total 166.67 g of 18K.
Mixing scenarios: Have 20 g of 22K and 30 g of 18K — what's the combined karat? Use Weight Arithmetic & Purity calculators together.
Cannot upgrade 18K to 24K by adding 22K gold: denominator (22 − 24) is negative while numerator (24 − 18) is positive → the calculator warns that this combination is geometrically impossible.
Jump to a ready-made conversion — useful for quick reference and sharing:
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