Karat to purity.

Answer

Percent gold = karat / 24 x 100, and fineness = karat / 24 x 1,000. 18k is 18/24 = 75% gold, stamped 750. 14k is 14/24 = 58.33% gold (583.3 parts per 1,000), and is usually stamped 585. 10k is 41.67% (stamped 417) and 24k is treated as 100% gold (stamped 999).

Worked example

Take 14k. 14 / 24 = 0.5833, so the piece is 58.33% gold and 583.3 parts per 1,000. The other 41.67% is alloy metal. The stamp commonly used for 14k is 585, a rounded standard value slightly above the exact 583.3.

How it works

Karat to percent: karat / 24 x 100. Karat to fineness: karat / 24 x 1,000. Fineness to karat: fineness / 1,000 x 24. The stamps listed are those given for each karat in the Fineness article: 8k 333, 9k 375, 10k 417, 12k 500, 14k 585, 15k 625, 18k 750, 20k 834, 22k 916, 23k 958 and 24k 999. A karat with no listed stamp, such as 16k or 21k, shows the exact calculated value only.

Sources and basis (opened 2026-10-08): Wikipedia, Fineness.

FAQ

What percent gold is 14k?

14k is 14/24 = 58.33% gold. The remaining 41.67% is other metals such as copper or silver.

What does 585 mean on gold jewelry?

585 is a millesimal fineness stamp meaning 585 parts per 1,000 are pure gold (58.5%). It is the stamp commonly used for 14 karat gold.

What karat is 750 gold?

750 means 75% gold, which is 18 karat (18/24 = 0.75).

Is 24k gold 100% pure?

24 karat gold is considered 100% gold. The stamp 999 is commonly used for it.

Why is 14k stamped 585 and not 583?

Exact 14/24 is 583.3 parts per 1,000, but the conventional standard stamp for 14 karat is 585, slightly above the exact 583.3, so a stamped piece can hold slightly more gold than the exact karat fraction.