916, 22K and KDM explained

Karat and fineness

Pure gold is too soft to wear every day. BIS puts it plainly: gold is too soft to withstand wear, so for jewellery it is always alloyed with another metal, such as copper, for strength. So every piece of gold jewellery is part gold and part something else, and purity is a way of saying how much of it is gold.

There are two ways to say it.

Karat counts in twenty-fourths. Pure gold is 24 carat. A 22 carat piece is 22 parts gold in 24. An 18 carat piece is 18 parts in 24.

Fineness counts in thousandths. IS 1417, the Indian Standard for gold jewellery, gives the gold content of each grade in parts per thousand. A fineness of 750 means 750 parts of gold in every thousand, which is 75%.

The two say the same thing in different units. Karat is the older word, and the one customers use. Fineness is more exact, and it is the number BIS checks.

The purity grades

The BIS hallmarking FAQ lists six grades that IS 1417:2016 permits for hallmarking gold jewellery and artefacts:

Hallmark	Fineness (per 1,000)	Gold content	Karat as a fraction
14K585	585	58.5%	14 ÷ 24 = 0.5833
18K750	750	75.0%	18 ÷ 24 = 0.7500
20K833	833	83.3%	20 ÷ 24 = 0.8333
22K916	916	91.6%	22 ÷ 24 = 0.9167
23K958	958	95.8%	23 ÷ 24 = 0.9583
24KS995	995	99.5%	24 ÷ 24 = 1.0000

Two points are worth knowing.

BIS’s summary of the standard gives each fineness as a minimum. A 916 piece must have at least 916 parts of gold in a thousand, not 916 on average.

BIS’s summary of IS 1417 (see Sources) also defines 24KF, fine gold of 999 and above, next to 24KS, standard gold of 995 and above. For jewellery, the grade in BIS’s list is 24KS (995).

Trade reports say Amendment No. 2 to IS 1417:2016 (2025) added 9K (375). BIS’s FAQ doesn’t list it yet, so check the current standard before hallmarking 9K.

Why 22K is stamped 916

Work out 22 parts in 24 and you get 0.91666…, or 916.67 parts per thousand. IS 1417 sets the 22K grade at 916. That is the number on the hallmark, so 22 carat gold is stamped 22K916, and “916 gold” has become the everyday name for it.

The same arithmetic gives the other grades. 18 in 24 is exactly 750. 14 in 24 is 583.3, but the standard sets 14K at 585, a little above the fraction. For the purity of a hallmarked piece, the fineness in the standard is what counts, not the fraction.

A hallmark shows both numbers together, carat and fineness, so the customer doesn’t have to do the sum. BIS asks registered jewellers to display how fineness relates to carat in the shop, which a simple chart like the table above does well.

What “KDM” meant

KDM is the trade name for gold jewellery joined with a solder that contains cadmium.

Most Indian jewellery is made of many small parts joined together. BIS’s own brief on hallmarking explains why that matters: Indian jewellery is mostly high-carat gold with numerous soldered joints of much lower carat, which makes the purity of a finished piece hard to judge without tests. Whatever the solder is made of, it is part of the piece.

Cadmium, whatever the trade name for it, is a health risk for the people who work with it. A study of small jewellery workshops in India that used cadmium under poor hygienic conditions, published in the journal Thorax in 2013, found that the workers had about ten times the urinary cadmium of jewellery sales staff. Three in four workers reported respiratory symptoms, against one in three of the sales staff, and the workers’ lung function was markedly lower.

IS 1417 limits it. According to BIS’s summary of the standard (summary PDF in Sources), IS 1417 sets maximum permissible limits for cadmium, checked by X-ray fluorescence (XRF) at the hallmarking centre. BIS’s guidelines for registered jewellers say that articles bearing any marking such as “KDM”, or any fineness or carat mark of their own, must not be sent to a hallmarking centre for hallmarking.

So a piece stamped “KDM” or “916” by its maker, without the BIS logo and a HUID, is not hallmarked. The stamp is the maker’s claim, not a BIS test.

How hallmarking tests a piece

At a BIS-recognised assaying and hallmarking centre, the jeweller’s pieces go through a fixed workflow: receipt and weighing, an XRF check, sampling, fire assay, and laser marking. The centre keeps the record of each step online, and BIS can monitor it as it happens.

Fire assay is the cupellation method set out in IS 1418. Pieces of the same fineness are sent as a consignment, and a sample is drawn from it and assayed. Only pieces that meet the standard get the BIS logo, the purity mark and a HUID.

BIS asks that each part of a pair, and each detachable part of a piece, be hallmarked with its own HUID. A part that can be removed is a part that can be swapped.

The checks continue after the sale. BIS draws samples of hallmarked jewellery from registered jewellers’ shops and tests them in its own referral labs. A customer can also have a hallmarked piece tested at any BIS-recognised centre for ₹200.

Why the rate you quote depends on purity

Gold value on a bill is the net weight of gold multiplied by the day’s rate for that purity. The purity decides how much fine gold the customer is paying for.

Take two pieces of the same weight, 10 g each:

• A 22K916 piece holds at least 9.16 g of fine gold.
• An 18K750 piece holds at least 7.5 g.

The 18K piece has about 18% less gold in it, so it takes a lower rate. Shops set their own rate for each purity, and the fineness tells you how much gold each rate is for.

This is also why BIS asks that the bill for hallmarked jewellery show the purity in both carat and fineness, next to the net weight of the gold. A customer can then check that the rate on the bill matches the stamp on the piece.

The free estimate maker on this site works out gold value, wastage, making, stones and GST from the weight and rate you enter, with your shop’s name on the estimate, ready to send on WhatsApp.

In 24Gold, an estimate at the counter starts from a tag scan, and the item tag carries the piece’s weight and purity, so the line on the estimate matches the piece in the customer’s hand.

Rules as published on 16 October 2026. Check the current BIS notifications for your district, or ask your BIS-registered hallmarking centre.