Gold Purity Converter (Karat) Calculator

Work out gold purity converter (karat) instantly with clear inputs, formula shown and shareable results.

About Gold Purity Converter (Karat) Calculator

Karat expresses gold content in twenty-fourths, so 18 kt is 18/24 or 75% gold - hallmarked as 750 fineness. A 10 g 18 kt ring holds 7.5 g of gold and 2.5 g of alloying copper and silver. Pure 24 kt gold is too soft for most jewellery, which is why alloys dominate.

Formulas

Purity

fraction = karat / 24

Fineness

fineness = purity x 1000, the hallmark figure

Worked example

With the default values below, Gold Purity Converter (Karat) Calculator returns Gold Purity of 75.000%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Gold purityaccepts 0–24 kt: 18 kt
Item massminimum 0 g: 10 g

Results

Gold Purity: 75.000%
Fineness (Parts Per Thousand): 750
Pure Gold Content: 7.500 g
Alloying Metal Content: 2.500 g

Step by step

1Values used
2Purity
3Fineness
4Gold Purity= 75.000
5Fineness (Parts Per Thousand)= 750
6Pure Gold Content= 7.500 g
7Alloying Metal Content= 2.500 g

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Which purities are standard?

24 kt (999), 22 kt (916), 18 kt (750), 14 kt (585) and 9 kt (375). Hallmarking law sets the permitted marks in each country.

Does higher karat mean better?

Purer, not better. Higher karat is softer and scratches more easily, so 18 kt is often the practical optimum for worn jewellery.