9K Gold and 18K Gold – What is the difference?

What is the difference between 9K and 18K gold? In the UK, jewellers tend to sell gold in these two purities. Which is better? In this guide, we explain the differences, including appearance, quality and price.

What are gold karats?

A karat is a unit of gold purity. It refers to the amount of pure gold there is in a piece of jewellery. The abbreviation for karats is the letter “K”.

How do karat measurements work?

One karat represents 1/24th of the gold content in a piece of jewellery or another precious object. At the top of this scale, 24K gold is 100% pure gold and at the lower end, 9K gold contains 37.5% pure gold.

Gold is mixed with alloy metals

You might be wondering what else is in your gold jewellery, if only a percentage of it is pure gold. The answer is that all gold that is used to make jewellery is mixed with alloy metals. Why? Because gold alone is a very soft metal. If used on its own, it would quickly bend out of shape.

Therefore, the gold that is used to make jewellery must always be mixed with hard alloy metals. For example, 18K gold, which contains 75% pure gold, also contains 25% of secondary metals like silver or copper.

A white gold ring being made by The Diamond Store

What gold purities are there?

Gold items come in various purities, as follows:

  • 9K gold is 37.5% pure gold
  • 14K gold is 58.3% pure gold
  • 18K gold is 75% pure gold
  • 22K gold is 91.6% pure gold
  • 24K gold is 100% pure gold

What is the difference between 9K and 18K gold?

The main difference between 9K and 18K gold is the gold content. At the lower end, 9K gold contains only 37.5% pure gold. At the higher end, 18K gold contains 75% pure gold.

The second difference is the price. 9K gold contains more alloy metals than gold. Alloy metals are cheaper than gold. Therefore, it is more expensive to make 18K gold, which contains more gold than alloy metals, than 9K gold.

Finally, you have to consider quality. 18K gold is heavier and feels more substantial and luxurious to the touch than 9K gold. Also, 18K gold items have a higher resale value than 9K gold items.