The little number stamped on gold jewellery, 9K, 10K, 14K or 18K, tells you how much of it is actually gold, and it affects the colour, the durability, the price and even how kind a piece is to sensitive skin. This guide explains what each karat means and how to choose the right one.
Gold karat, shown with a capital K, is how much pure gold is in the metal, measured in parts out of 24. So 18K is 75 percent gold, 14K about 58 percent, 10K about 42 percent and 9K 37.5 percent, with stronger metals making up the rest. Higher karat means a richer colour and more pure gold but a slightly softer metal, while lower karat is harder and more affordable. All of them are solid gold.
What does karat mean?
Karat, written with a capital K, measures the purity of gold in parts out of 24. Pure gold is 24K, so if 18 of those 24 parts are gold the metal is 18K, and the remaining parts are stronger metals like copper, silver, zinc or palladium. In New Zealand you will also see purity written as a number with "ct", so 9ct, 10ct, 14ct and 18ct mean the same as 9K, 10K, 14K and 18K. The reason gold is mixed at all is that pure 24K gold is too soft to hold a shape or a stone in everyday wear, so it is alloyed to make it durable. Every karat below is still solid gold, just with a different balance of gold to other metals.
| Karat | Pure gold, and character |
|---|---|
| 18K | 75 percent gold. The richest colour and highest purity in common use, a little softer. |
| 14K | 58.3 percent gold. A strong balance of good colour and durability. |
| 10K | 41.7 percent gold. Hard-wearing and affordable, with a paler tone. |
| 9K | 37.5 percent gold. The hardest and most affordable, palest in colour. |
9K gold
9K gold is 37.5 percent pure gold, hallmarked 375, and it is the most affordable of the common karats, which makes it a popular everyday choice in New Zealand, the United Kingdom and Australia. With the most alloy in the mix it is hard and stands up well to daily knocks, though that same high alloy content makes it a little more brittle and gives it the palest, most muted yellow of the four. It is a sensible, durable choice for pieces worn hard, as long as you are happy with a lighter colour.
10K gold
10K gold is 41.7 percent pure gold, hallmarked 417, sitting just above 9K. It is hard-wearing and affordable like 9K, with a fractionally warmer colour, and it is the minimum purity that can legally be sold as gold in the United States, where it is common. It makes a good everyday metal for anyone who wants durability and value, with a touch more gold in the mix than 9K.
14K gold
14K gold is 58.3 percent pure gold, hallmarked 585, and it is the sweet spot for many people. It carries clearly more gold than 9K or 10K, so its yellow is warmer and richer, yet it keeps plenty of the hardness that makes gold practical for everyday wear. That balance of good colour, durability and value is why 14K is the most popular choice for fine jewellery worn every day, and it is gentle on skin thanks to its lower alloy content.
18K gold
18K gold is 75 percent pure gold, hallmarked 750, and it is the purest gold in common jewellery use. That high gold content gives it the deepest, most luxurious yellow and the greatest sense of quality, and because it holds so little alloy it is the kindest of all to sensitive skin and the least likely to react or tarnish. The trade-off is that more pure gold means a softer metal, so an 18K piece, and especially its claws or fine details, rewards a little more care. It is the choice for a special piece where colour and purity matter most.
Which karat is best for you?
There is no single best karat, only the one that fits the piece and how you will wear it. The choice mostly balances colour and purity against hardness and price.
For pieces worn hard every day, 9K, 10K and 14K are the most durable, with 14K giving the best mix of colour and toughness. For the richest colour, the highest purity and the kindest metal for sensitive skin, choose 18K, and treat it a little more gently. On a budget, 9K and 10K go furthest. Whichever you pick, it is solid gold, so it holds its colour and lasts.
Colour aside, the difference between 9K and 14K is subtle enough that most people cannot pick it once a piece is on, so let durability, budget and the warmth of colour you want guide you. The other big decision is the colour itself, yellow, white or rose, which our guide to yellow, white and rose gold covers, and it is worth knowing that all of this assumes solid gold rather than plated. This sits within our wider guide to gold. You will find solid gold in a range of karats across our earrings, rings and necklaces and pendants.
