9ct gold is 37.5 percent pure gold. 18ct gold is 75 percent pure gold, exactly double. Both are genuinely used across South African fine jewellery, and the differences in purity, colour, hardness, and cost are real, if often overstated in either direction. Here's what each actually means for your ring.
Purity: 18ct is more gold, 9ct is harder
The caratage of gold describes what proportion of the alloy is pure gold. 18ct gold is 18 parts out of 24 pure gold, 75 percent, hallmarked 750. 9ct gold is 9 parts out of 24, 37.5 percent, hallmarked 375. The rest, in both cases, is alloying metal, copper, silver, palladium, or zinc depending on the alloy and the colour you're after.
Higher gold content gives a richer, more saturated colour in yellow and rose gold, and slightly lower hardness, because pure gold is soft and it's the alloying metals that add hardness. 9ct, with roughly double the proportion of alloying metals, is noticeably harder and more scratch-resistant than 18ct.
Colour: the difference is real, and bigger than in most gold comparisons
The visual gap between 9ct and 18ct is most obvious in yellow and rose gold, since higher gold content produces a warmer, more saturated tone. 18ct yellow gold has a rich, deep colour; 9ct yellow gold is still clearly yellow but noticeably more muted, with less depth. 18ct rose gold carries a distinctly pink tone from its higher copper content; 9ct rose gold reads cooler and less intensely pink. In white gold, the difference matters far less, since both grades are rhodium plated and the plating, not the underlying gold content, determines the visible colour.
Durability: 9ct is genuinely harder
9ct gold's higher alloy content makes it harder than 18ct, so it resists surface scratching more effectively, a real practical advantage for daily wear. If you work with your hands or are generally hard on jewellery, 9ct may hold up better over the years. Prong tips maintain their structure slightly better in 9ct over very long stretches too, thanks to that greater hardness. That said, for most people in normal daily conditions, either grade will last decades without structural concern, and both develop a natural patina over years of wear that many people find attractive.
Cost: the gap is meaningful, not marginal
18ct contains roughly double the pure gold of 9ct, so it costs more per gram, and because the gold content gap here is so much larger than in most karat comparisons, the price difference between an 18ct and a 9ct version of the same design is genuinely worth factoring into your decision, not just a rounding error on the total. We'll confirm the exact price difference for any specific design at the quote stage. For a full ring, the centre stone, setting, and manufacturing also make up a meaningful share of the total cost, but the metal itself is not a small line item here.
Which to choose
Our pricing is built around 9ct as the accessible starting point, moissanite from R13,995 and lab diamond from R24,995, both in 9ct gold, and 9ct has long been a familiar standard in South African jewellery for exactly that reason: it's durable, it's the traditional local choice, and it keeps the ring affordable without compromising on the centre stone. 18ct is available as an upgrade for anyone who wants the richer colour and higher purity, particularly in yellow or rose gold where the visual difference is most noticeable. Neither is the objectively correct choice, it comes down to whether colour richness or cost and scratch resistance matters more to you.
Frequently asked questions
Is 9ct or 18ct gold better for an engagement ring?
Neither is objectively better. 9ct is harder, more affordable, and the traditional South African standard. 18ct offers richer colour and higher purity. The right choice depends on your priorities.
What is the hallmark for 9ct and 18ct gold?
9ct is hallmarked 375, for 375 parts per thousand pure gold. 18ct is hallmarked 750, for 750 parts per thousand.
Is 9ct gold significantly cheaper than 18ct?
Yes. Because 9ct contains roughly half the pure gold of 18ct, the price gap is more significant than most karat comparisons, worth genuinely factoring into your decision rather than treating as incidental.
Does 18ct gold scratch more easily than 9ct?
Yes. 18ct is softer because it has less alloying metal, and pure gold itself is soft. 9ct's higher alloy content makes it more scratch-resistant. In normal daily wear, both hold up well.
Which gold do you build your pricing around?
9ct. It's our starting point for moissanite from R13,995 and lab diamond from R24,995, with 18ct available as an upgrade on request.
See exact pricing for both grades on our prices page, browse yellow, rose, or white gold options, or start a free design consultation and we'll confirm the price difference for your specific design in both grades.