22K, 24K and 18K gold: purity and hallmark explained

What karat means

Karat is a measure of how much of a piece is pure gold, out of 24 parts. 24K is pure gold. 22K has 22 parts gold and 2 parts other metals, usually copper or silver, which make it harder.

Karat and carat are different

Karat measures gold purity. Carat measures the weight of gemstones such as diamonds. A "22 karat" ring is 91.6% gold, while a "1 carat" diamond weighs 0.2 grams.

How to read a BIS hallmark

Hallmarked gold jewellery sold in India carries marks stamped by a licensed centre:

• The BIS logo.
• A purity grade, such as 22K916.
• A six-character alphanumeric HUID, the Hallmark Unique Identification number.

The HUID is unique to each piece. You can check a HUID using the BIS Care app. Jewellery bought before mandatory hallmarking may carry older marks or none at all.

Why purity changes your price

Purity is one of the three numbers that set your price, along with weight and rate. A piece marked 22K may test slightly higher or lower in practice, so a buyer tests it again. Read how old gold is valued for the full formula, and how gold purity is tested for the methods.

No hallmark? You can still sell it

Old jewellery without a hallmark can be sold. The purity is tested at the time of sale and written on your slip.