9ct Gold vs 18ct Gold
by Kate Reid
January 10, 2025 / Jewellery Buying Guide, Learn About Metals
One of the most common questions we receive from couples planning their custom engagement or wedding rings is "What is the difference between 9ct and 18ct gold?" This guide will walk you through the main characteristics that set them apart.
You may be wondering what exactly ‘ct’ or sometimes seen as ‘K’, refers to. The ‘carat’ of a metal denotes the percentage of pure gold in the alloy, with 9ct being 37.5% and 18ct 75% pure gold.
Gold in its purest form is too soft to be used in fine jewellery, so it is commonly mixed with other metals to increase its strength and durability, as well as to create unique colours like rose gold and white gold.
Colour
Metal Content
So which metal is best? Read more to learn about their durability for everyday wear and their ability to resist tarnish from everyday chemicals.
Durability
9ct
Less dense and likely to wear away over time.
18ct
More resistant to hard knocks. Lasts longer with everyday wear.
9ct gold contains a larger percentage (62.5%) of non-precious metals than 18ct gold (25%). A common misconception is that this makes 9ct more durable of a metal for everyday wear, but this is not actually the case. The other metals used result in 9ct gold being less dense which means it has a tendency to wear away much more quickly. 18ct gold is longer wearing and more resistant to damage, making it the recommended choice for everyday wear.
Resistance to Tarnish
9ct
More likely to tarnish from chemicals like chlorine, hairspray and perfume.
18ct
More resistant to tarnish due it’s higher Gold content. Gold is the least reactive of all metals.
In its pure form, gold is one of the least reactive elements. More than half the content of 9ct gold is made up of other elements that are more prone to tarnishing and eroding. As a consequence, 9ct is more likely to discolour or be damaged by exposure to chemicals. Exposure to chemicals and perspiration can mean your 9ct jewellery may appear dull and discoloured.
Summary
At the end of the day, 18ct gold is worth the higher price. It has twice the gold content of 9ct making it superior in terms of durability and performance.
This does not mean that 9ct is not a fine choice for certain jewellery. In fact, 9ct can be a great choice for dress rings, earring and pendants that are not worn every day. For pieces such as engagement rings and wedding rings, 18ct is a much more durable and long-lasting choice.
It is also important to outline the difference between 18ct white gold and platinum when discussing which metals are more suitable for certain designs. Platinum is a white metal that is used almost in its pure form (95%). It is also extremely dense making it heavier than white gold. Platinum is renowned for its hard and long-wearing qualities, which is what makes it so ideal for engagement rings with very fine settings. The other bonus about Platinum is that because it is white in its natural state there is no need to have it rhodium plated as is the case with white gold. What is the catch? Platinum is typically more expensive than 18ct gold. To understand the differences between platinum and white gold, read our comparison here.
Interested in more information about how to choose your engagement or wedding rings? Click here to read our engagement or wedding ring guides:
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