The Facts: 9ct vs 18ct

by Kate Reid
February 1, 2019 / Jewellery Buying Guide,Learn About Metals

The Facts: 9ct vs 18ct

One of the questions we often get asked is what is the difference between 9ct and 18ct. Below we have explained what the differences are and the pros and cons of these two options.

You may be wondering what exactly the ‘ct’, 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. Many come in and ask if it is true that 9ct gold is harder than 18ct gold. This is a misconception. In the case of white gold, the reverse is true, 18ct white gold in considerably harder than 9ct white gold. In yellow and rose golds, the hardness between the two is virtually the same.

Gold, in its pure form, is one of the least reactive elements so 9ct gold, having been mixed with a higher percentage of other elements, is consequently more likely to be damaged by exposure to chemicals, such as chlorine for example. Exposure to chemicals and perspiration can mean your 9ct jewellery may appear dull and discoloured. 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.

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  1. Balwinder Kaur says:

    Hey team
    Actually I am wondering to buy a gold chain with 18ct or 22ct for my husband . Not too heavy , just the normal weight n size. Please lemme know if u deal in that too , thanks much !

  2. Janna Foy says:

    Thank you for your information.What is the average price for 14kt 18in solid rope chain necklace?

  3. Timothy says:

    Hi! What is the ave price for 21ct yellow gold curb chain, 60cm necklace?

    • Kate Reid says:

      Hi Tim,

      Thanks for commenting! We only supply chains in 18ct or 9ct gold, 21ct is not a common alloy. Would it suit you to come into one of our studios (either Melbourne or Sydney) so that we can show you some options?

  4. Glyn Gatland says:

    Can you tell me what the weight of a 9ct and an 18ct yellow gold D shaped plain slave bangle would likely to be.



    • Kate Reid says:

      Hi Glyn,

      The weight of a bangle is very much dependent on the width and thickness. If, for example, if a 9ct bangle weighs 15 grams, the same dimension bangle would weigh 21 grams in 18ct gold.

  5. Glyn Gatland says:

    Kate. Thank you for your response.
    In my initial question I failed to say that I was looking for a D shaped bangle about 4mm wide.
    Can you give me a ball park figure for one in 9 and 18ct yellow gold
    Regards Glyn Gatland

  6. Zoe says:

    I want to buy a white gold wedding ring but I’m unsure if I’m better off buying 9, 14 or 18ct. Also will I need to get the rhodium plating done regularly?

    • Kate Reid says:

      Hi Zoe,
      We always recommend 18ct white gold unless it is going to be worn next to an engagement ring that is either 9 or 14ct. If two rings are going to be worn together, they should be the same alloy.
      Rhodium plating is a surface treatment that wears off over time, the rate of this depends on how well you take care of the ring. Most people have their rings replated every 1-3 years.

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