22K vs 24K vs 18K gold — purity, price and what each is used for

Karat is a measure of how much of an alloy is gold. Pure gold is 24 karat; 22 karat is 22 parts gold in 24, and so on. The BIS hallmark writes the same thing as fineness, in parts per thousand: 24K999, 22K916, 18K750, 14K585 (BIS, Hallmarking overview). The rest of the alloy is copper, silver, zinc or other metals that make the gold harder and change its colour.

The purities you will meet

Mark	Gold content	Where you see it
24K999	99.9%	coins, bars, the benchmark rate
24K995	99.5%	some coins and bars
23K958	95.8%	some traditional jewellery
22K916	91.6%	most Indian jewellery
20K833	83.3%	less common jewellery
18K750	75%	stone-set and designer jewellery, watches
14K585	58.5%	lighter everyday jewellery

Pure gold is soft. It scratches and bends, and it cannot hold a stone securely, which is why coins and bars are 24K and jewellery is 22K or lower. The lower the karat, the harder the piece and the less gold it contains per gram.

Why the rates move together

The IBJA publishes a rate for each fineness twice a day. Those rates are not set independently: the 999 rate is the reference, and the others follow it by their gold content. A 22K rate is close to 916 ÷ 999 of the 24K rate, an 18K rate close to 750 ÷ 999 of it. The gold pages on this site show the IBJA figures for 24K, 22K and 18K side by side, and you can see the fractions hold from day to day.

What a jeweller charges per gram for 22K is therefore a known fraction of the 24K rate plus the shop’s margin. If a shop’s 22K rate is much more than 91.6% of the day’s 24K rate, the difference is margin, not purity.

Which purity for what

Investment in metal — coins and bars — is almost always 24K (999 or 995). You pay for gold, not for work, and the making charge is a small flat amount. Resale is by weight and purity, so the closer to pure, the simpler the valuation.

Everyday and wedding jewellery in India is mostly 22K. It keeps most of the gold value, takes the traditional yellow colour, and is hard enough for bangles, chains and plain rings. Making charges are a percentage of a large gold value, so they matter.

Stone-set and fine designer pieces are often 18K, sometimes 14K. The harder alloy holds stones and thin settings; the piece has less gold per gram, so its gold value at resale is lower and the design carries more of the price.

The price of a piece, by purity

For the same weight, a 22K piece contains about 92% as much gold as a 24K piece, an 18K piece about 75%. When a piece is sold back, the buyer pays for the gold content at the day’s rate for that fineness, less the buyer’s deductions. The making charge and any premium for design are not recovered. So a 24K coin loses the least on resale, 22K jewellery a little more, and 18K jewellery the most relative to what was paid.

None of this makes one purity better than another; it is a trade between gold content, hardness and the kind of piece you want. What matters is that the purity on the hallmark, the purity on the bill and the rate applied all agree — the guides on the hallmark and HUID and on reading the bill show how to check each.