Jewellery knowledge · 02 Oct 2026 · 2 min read

Reading gold hallmarks: what 999, 750 and 585 mean

The number stamped on jewellery tells you how many parts per thousand are pure gold. Understand it and you can work out the gold value of what you buy.

Written by Kim Bảo Minh Châu

Close-up of the 24K Golden Grain ring with its rice-ear motif

Inside a ring, on a necklace clasp or an earring post there is often a small number: 999, 750, 585. It is the gold purity, in parts per thousand.

Conversion table

Parts per thousand	Karat	Gold content	Common name
999.9	24K	99.99%	9999 gold
999	24K	99.9%	999 gold
916	22K	91.6%	22K gold
750	18K	75%	18K gold
585	14K	58.5%	14K gold
416	10K	41.6%	10K gold

How karats work: 24K is near-pure gold and each karat is 1/24. 18K means 18 parts gold in 24 parts metal, or 75%.

Labelling rules

Circular 22/2013/TT-BKHCN allows purity in parts per thousand or in karats with a K. Actual purity may not be below the stated value. Gold measuring between grades drops to the grade below: 21.5K is labelled 21K. Pieces combining parts of different purity are labelled by the lower one.

The 24K Twisted Rope ring, stamped 999.9 on the band

Work out the real gold

Pure gold = weight × purity.

A 24K ring of 1 chỉ: 1 × 0.9999 ≈ 1 chỉ of pure gold.
An 18K ring of 1 chỉ: 1 × 0.750 = 0.75 chỉ.
A 14K necklace of 2 chỉ: 2 × 0.585 = 1.17 chỉ.

Multiply by the day's 9999 price for the metal value. The rest of the selling price is labour and stones.

Why jewellery uses 18K

24K is soft, dents easily and holds stones poorly. Alloying with silver, copper, zinc or palladium in different ratios makes 18K harder, keeps prongs secure and creates white and rose tones. Kim Bảo Minh Châu sets diamonds in 18K; plain everyday pieces and savings gold are 24K.