Gold alloy calculator: lower the karat without guessing
Enter the weight and karat of your gold and the karat you want. You get the grams of alloy to add, and how much of it is silver and how much copper for the color you are after.
Free, no sign-up. Everything is calculated in your browser.
Alloy calculator
The pure gold stays the same: we only work out the metal to add.
Fine silver 50 % · Copper 50 %
7.14 g
3.57 g of fine silver and 3.57 g of copper for 17.14 g of 14K gold.
- Fine silver
- 3.57 g
- Copper
- 3.57 g
- 24K gold to melt
- 10.00 g
- Final weight
- 17.14 g
Pure gold in the melt: 10.00 g
How to work out the alloy to lower the karat
- 1.Choose whether you start from the gold you have or the final weight you need.
- 2.Enter the weight in grams and the karat of the gold you will melt.
- 3.Choose the karat you want: 22K, 18K, 14K, 10K or whatever you work in.
- 4.Pick an alloy color or set your own silver-to-copper ratio.
- 5.Weigh out the fine silver and copper the calculator gives you and melt them with the gold.
The gold alloy formula
Lowering the karat never changes the pure gold: you only add metal that is not gold. So the final weight is your gold's weight times its karat divided by the karat you want, and the alloy is the difference between the two weights.
Example: 10 g of 24K gold made into 14K. 10 × 24 ÷ 14 = 17.14 g of 14K gold, so you add 7.14 g of alloy.
The alloy sets the color. Half silver and half copper gives a classic yellow; more copper turns the gold rose and then red; all silver leans green. White gold uses ready-made palladium or nickel whitening alloys.
If your starting gold is not 24K, it already carries alloy of its own; the calculator only gives you what to add. Melt with borax, stir well and let it cool before rolling.
Frequently asked questions
How much alloy is in 14K gold?
14K gold is 14 parts gold and 10 parts alloy out of 24. Every 10 g of pure gold needs 7.14 g of alloy to become 14K, for a 17.14 g ingot.
How do I bring 18K gold down to 14K?
Multiply the weight by 18 and divide by 14; the difference is the alloy. For 20 g of 18K: 20 × 18 ÷ 14 = 25.71 g in the end, so 5.71 g of alloy.
What silver-to-copper ratio makes yellow gold?
A common starting point is half fine silver, half copper. For a paler yellow raise the silver to 60 or 65 %; for a warmer one raise the copper. Every workshop tunes its own recipe.
And rose or red gold?
Rose gold alloy is mostly copper, around 75 % copper; red gold is nearly all copper. The more copper, the harder and redder the metal.
Can I use it for white gold?
It gives you the grams of alloy to add, but white gold is not made with silver and copper: it uses a palladium or nickel whitening alloy. Set that alloy to 100 % with the custom ratio.