Gold Karat vs Gold Fineness: Understanding 999, 916, 875 and 750

Gold purity is often described in two different ways. One jeweller may call a piece 22K gold, while another may stamp it 916. An 18K ring may carry a 750 mark. These numbers are not competing standards. They are two ways of expressing how much pure gold is contained in an alloy.

Understanding both systems makes it easier to compare jewellery, read hallmarks and estimate the underlying gold content of an item. It also helps avoid a common mistake: assuming that a number stamped on gold is a weight or a price when it is usually a purity mark.

—

What does karat mean?

Karat, written as K in many markets, measures gold purity on a 24-part scale. Pure gold is described as 24K. If an alloy is 18K, 18 of its 24 parts are gold and the remaining six parts are other metals.

The basic calculation is:

Gold purity percentage = Karat ÷ 24 × 100

So 18K gold is 18 ÷ 24 = 75% gold. The balance can include metals such as silver, copper, zinc, or palladium, depending on the colour, strength, and manufacturing requirements of the jewellery.

The World Gold Council explains that caratage measures the purity of gold alloyed with other metals and notes that 18 carat gold contains 75% gold.

—

What does fineness mean?

Fineness expresses precious-metal content in parts per thousand. A fineness of 750 means that 750 parts out of every 1,000 are gold, or 75%. A 916 mark means approximately 91.6% gold.

This is why fineness markings are often called millesimal fineness. The system is especially useful on hallmarks because it gives a direct numerical indication of precious-metal content.

—

How karat and fineness correspond

—

What does 999 gold mean?

A 999 mark means 999 parts gold per 1,000, or 99.9% purity. It is commonly associated with 24K gold. In practice, extremely pure refined gold may also be described as 999.9, meaning 99.99% purity.

The difference between the theoretical 100% represented by 24 out of 24 parts and real-world fineness markings reflects the fact that refined gold can contain very small residual impurities. For everyday buying and pricing, 999 and 999.9 are both treated as very high-purity gold, but the exact specification should still be checked when buying bullion.

—

What does 916 gold mean?

A 916 mark means the alloy contains 916 parts gold per 1,000, or 91.6%. This corresponds closely to 22K gold because 22 ÷ 24 equals approximately 91.67%.

22K gold is widely used for jewellery in markets where buyers prefer high gold content while still wanting more durability than near-pure 24K gold normally provides.

—

What does 875 gold mean?

A fineness of 875 means 87.5% pure gold. That corresponds exactly to 21K because 21 ÷ 24 = 87.5%. It is frequently encountered in jewellery markets where 21K pieces are common.

—

What does 750 gold mean?

A 750 mark means 75% of the alloy is gold. That is the fineness equivalent of 18K gold. The remaining 25% consists of other metals, which can alter hardness, colour, and wear characteristics.

Because 18K contains less pure gold than 22K or 24K, its underlying metal value per gram is lower when all other conditions are equal. However, a finished 18K jewellery item can still have a high retail price because design, brand, craftsmanship, stones, and making charges are separate from the value of the gold itself.

—

Why is gold mixed with other metals?

Pure gold is relatively soft. Alloying it with other metals can make jewellery more durable and can also change its colour. This is how jewellers produce variations such as yellow gold, rose gold and white gold.

The presence of other metals does not automatically make an item inferior. The appropriate purity depends on how the piece will be used, the local market and the buyer’s priorities. A lower-karat ring may be more resistant to everyday wear, while a high-karat piece contains more gold by weight.

—

Is a fineness mark the same as a full hallmark?

Not always. A number such as 750 or 916 can indicate claimed fineness, but hallmarking rules vary by country. In jurisdictions with formal hallmarking systems, a legally recognised hallmark can include additional information showing who submitted the item and which assay office tested it.

For example, UK government hallmarking guidance states that a full UK hallmark includes a sponsor or maker mark, a metal-and-fineness mark and an Assay Office mark. Local requirements differ, so buyers should check the rules that apply where the item is being sold.

—

How to convert karat to fineness yourself

You can estimate the equivalent fineness by dividing the karat by 24 and multiplying by 1,000.

Fineness ≈ Karat ÷ 24 × 1,000

• 18K: 18 ÷ 24 × 1,000 = 750
• 21K: 21 ÷ 24 × 1,000 = 875
• 22K: 22 ÷ 24 × 1,000 ≈ 916.7 (commonly represented as 916 for jewellery)

—

Why this matters when checking gold prices

The price of one gram of 18K gold should not be compared directly with one gram of 24K gold without adjusting for purity. The 24K gram contains more pure gold. This is why GoldRates displays separate reference values for different purities rather than treating every gram of gold as identical.

When comparing an item with the market, start with the live purity-based rates on GoldRates.com, then account separately for any dealer premium, making charge, tax or resale deduction.

—

The key takeaway

Karat and fineness describe the same basic idea: how much pure gold an alloy contains. Karat uses a 24-part scale, while fineness uses parts per thousand. That is why 24K corresponds to roughly 999 or 999.9, 22K to 916, 21K to 875 and 18K to 750.

Once you understand that relationship, jewellery stamps and gold-price comparisons become much easier to interpret. The purity mark tells you the proportion of gold in the alloy. It does not, by itself, tell you the weight, retail price or resale value of the item.