Gold Purity Calculator

Divide the karat number by 24 and multiply by 100. For example 18 karat is 18 / 24 * 100, which is 75% pure gold. The calculator uses the same formula and shows the percent to four decimal places.

Fineness states purity in parts per thousand. A fineness of 750 means 750 parts gold per 1000, equal to 18 karat or 75% pure. The tool derives it as karat / 24 * 1000 and rounds to two decimals.

14 divided by 24 is 0.583333, so 14 karat is 58.3333% pure and 583.33 fineness. Hallmark stamps round this down to 585 or 583 for convenience, but the true math is not a whole number.

24 karat is the definition of pure gold, so this tool treats it as exactly 100%. In practice refined bullion is stamped 999 or 9999 fineness because trace impurities always remain, which works out to about 99.9% or 99.99%.

Yes. Switch the Convert dropdown to From percent or From fineness. Enter 75 percent and you get 18k and 750 fineness; enter 750 fineness and you get 18k and 75%. Any of the three values can be the starting point.

Yes. The engine expects exactly one of karat, percent or fineness and derives the rest. The interface enforces this by showing a single input field for whichever mode you select.

Karat runs from 0 to 24, percent from 0 to 100 and fineness from 0 to 1000. A value must be a positive number within its range, otherwise the calculator asks you to enter a value in range instead of showing a result.

No. It converts between the three ways of expressing a purity you already know. To find the true purity of a physical piece you need an assay, an electronic tester or an acid test; this tool cannot measure metal.

No. Every conversion is computed locally in your browser, so the values you type are never uploaded or stored.