22 Karat Gold
91.6% gold. The Indian standard for traditional jewellery, and what a 916 hallmark means.
22K is the default for Indian gold jewellery, and the reason 916 is stamped on so much of it: 91.6% is the same number expressed as parts per thousand.
It keeps the rich yellow most Indian buyers expect, while being just hard enough to work into chains, bangles and temple pieces.
It is still soft by international standards, so 22K is a poor choice for a ring with a fragile stone or for anything that takes daily knocks.
When you are buying
This is the right purity for traditional pieces bought partly as savings, since resale is calculated on gold content. It is the wrong purity for a diamond or polki setting, where the prongs will loosen.
916 Gold
The hallmark number for 22 karat gold, meaning 91.6% pure. The same thing as 22K.
Karat
The purity of gold, measured in twenty-fourths. 24K is pure gold; 22K is 22 parts gold to 2 parts other metal.
18 Karat Gold
75% gold. Harder and more durable than 22K, which is why stone-set and Western-style jewellery uses it.
24 Karat Gold
Pure gold, 99.9% fine. Too soft for jewellery that gets worn, so it is bought as coins and bars.
Hallmark
An official stamp certifying precious metal purity. In India, BIS hallmarking is mandatory for gold jewellery.