9k vs 18k gold: which should I choose?

When investing in a piece of gold jewellery, deciding which karat value to choose will inevitably be part of your decision-making process. Internationally, 14 karat gold is most recognised. In the UK, however, we do things a little differently, with 9 karat and 18 karat gold the two main options. 

Often abbreviated to 9k and 18k, the karat value of gold determines not only the durability and price of a jewel. It also has a significant impact on its appearance. Understanding the difference between them will help you make the most informed choice.

9k vs 18k gold: what’s the difference between them?

The 9 and 18 refer to the purity of the gold. In 18k gold, 18 of the 24 parts are pure gold, mixed with six parts of additional metals like copper, silver and zinc, creating an alloy. The same applies for 9k gold, which comprises 9 parts pure gold. Why is gold mixed with different metals to form an alloy? Put simply, pure gold is a naturally soft metal and combining it with additional metals makes it stronger. 

Because 9k gold is mixed with a higher percentage of other metals, it is more robust and durable. This also means it is less valuable than 18k gold. On the other hand, 18k gold, which is brighter, richer, warmer and has a greater intrinsic value, is a naturally softer metal. This makes it more prone to scratching.

The difference in colour and appearance of 9k vs 18k gold is quite pronounced and another important factor to consider. 9k gold tends to be paler yellow in colour, while 18k gold offers the traditional, deeper yellow hue most frequently associated with gold. It also appears more lustrous and contrasts beautifully with diamonds. 

What does Sophie recommend: 9k or 18k gold?

This really depends on how you intend on wearing your SB jewellery. We usually recommend 9k yellow gold for everyday pieces that you aren’t too precious about. Harder than 18k gold, it is able to withstand active holidays, beach parties and midnight swims. It is also the best choice for layering alongside other pieces of jewellery, such as chunky chains and bracelets, which rub against each other. 

As a softer metal, 18k gold might not be as tough as 9k gold, but it does offer the rich, opulent “true gold” colour that is inherently luxurious. It also holds gemstones better, with the hardness of 9k gold making it a difficult metal to achieve a perfect, polished finish. Because of its higher gold content, it also has a reassuring solidity to it and, unlike 9k gold, doesn't tarnish. And while it is certainly a bigger investment, it will be worth more in the long term. This is why all Sophie Breitmeyer engagement rings are crafted in 18k gold.  

Which brings us on to affordability. One of the main reasons people opt for 9k jewellery over 18k gold is because it is a more cost-effective way of owning a piece of gold jewellery. If you aspire to have a collection of chains or bracelets to pick and choose from, Sophie recommends 9k gold. For a jewel as important and emotive as an engagement ring, she advocates for 18k gold every time.