9ct or 18ct gold: which should you choose?

When someone is choosing a piece in gold, one question comes up more than any other: 9 carat or 18 carat?

Engagement ring, wedding band, necklace or a bespoke commission — the metal changes how the piece looks, how it ages, and what it costs. Here is what actually separates the two.

What is the difference?

It is how much pure gold is in the alloy. 18ct gold (750) is 75% pure gold. 9ct gold (375) is 37.5% pure gold.

The rest is other metals — silver, copper, palladium. They give the alloy its strength and shift its colour. That is why 18ct pieces are hallmarked 750 and 9ct pieces 375.

Is the colour different?

Yes. 18ct has a richer, deeper, warmer colour, because there is more pure gold in it. 9ct tends to be slightly paler, particularly in yellow alloys.

The difference is subtle. It is obvious when the two are side by side, and easy to miss when they are not.

Which is more durable?

Both are perfectly suited to fine jewellery, and the common assumption here is wrong.

9ct contains more alloying metal, so people conclude it must be harder. Measured hardness does not bear that out — most 18ct alloys are as hard, and often harder. What 18ct also does is hold its colour considerably better over the years.

For a ring worn every day, either works when it is properly made.

What about price?

Price follows the pure gold content, so 18ct costs more — it contains twice as much of it. On some bespoke projects, 9ct is what makes a solid gold piece possible within a tighter budget.

Which would I use for an engagement ring?

I work in both.

For a ring meant to be worn for a lifetime I often suggest 18ct: richer colour, higher intrinsic value, better colour retention. But 9ct is a genuinely good option when the budget matters, and it compromises neither the quality nor the look of the piece.

And if you bring in an old piece, its gold can often be reused — what's possible is here.

If what you have is inherited and unworn, there are five honest answers here, and what actually happens to a piece on the bench is set out here.

How I'd decide

Choose 18ct if you want the more precious metal, you prefer the deeper colour, or the piece is meant to pass down a generation.

Choose 9ct if you are working to a budget, you want the value for money, or you want more of the budget to go into the stone and less into the metal.

In short

There is no right or wrong answer. Both make strong jewellery that stands up to daily wear. What matters is which metal suits your taste, your life and your budget.

Undecided? Come to the boutique-atelier in Carouge and I'll show you the two golds side by side. It is much easier to choose with both in front of you.