What is a carat? How many carats are in gold? How big is a one-carat diamond? In this master style, we explain the difference between gold and diamond carats and help you to understand the meanings of each.

What is a carat?

If you are jewellery shopping, you may have seen the word “carat” used in two different ways. It’s also spelled differently depending on which country you shop from. Let’s cut through the confusion…

What does carat mean? The word “carat” is thought to come from the Greek word for carob seed. It is derived from a measurement of weight.

What does carat mean in diamonds?

If used to define a gemstone, the meaning of “carat” is close to the original word. It is a unit of weight that affects the value of the stone.

How much does a carat weigh? It was around 205mg for many years until, in 1907, the International Committee of Weights and Measures decided to set the metric carat at 200mg. This was widely adopted to avoid confusion and assist in the world trade of diamonds and gemstones. Today, 200mg (0.2g) is one carat, and it is pided into “points” of 0.02g. So you may see a diamond referred to in terms of a carat (10 carats = 2g) or, if it is smaller than a carat, it might be described in terms of points (8 points = 0.16g).

What is “carats” in gold?

Here’s where it gets confusing. In relation to gold and other metals, a “carat” has a completely different meaning.

The Karat or Carat system measures metal purity as a fraction. It tells you how many parts (of a total of 24) are pure. 9-carat gold is the minimum accepted standard of gold in the UK, and 24 carat is the purest gold. To add to the puzzle, the Carat number is not usually stamped on the metal. That number is linked to the percentage of pure gold.

Did you know? The English carat measure is visible into four grains, each of which is divided into four quarts.

How many carats is pure gold?

  • 24 karat or 24-carat gold is the purest form of gold, although it is defined as being 99.9% pure since it’s virtually impossible to eliminate all impurities.
  • This form of gold is soft and malleable. It’s usually found in bullion bars and coins. It’s not really suitable for making jewellery, because it is not hard enough to withstand a lot of wear.
  • 22 karat or 22-carat gold is 91.6% pure. It consists of gold blended with alloys such as zinc, silver or copper.
  • These are added to increase hardness and improve scratch-resistance. 22-carat gold is beautiful and highly tarnish-resistant.
  • This type of gold is perfect for luxury jewellery, and a top choice for investors.
  • 18 carat or 18-carat gold is 75% gold. This is the highest purity for white gold, which requires a substantial amount of silver and/or platinum to obtain the white colour.
  • 12 karat or 12-carat gold is made up of 12 parts gold, 12 parts another metal. It’s therefore 50% pure gold.
  • 9 karat or 9-carat gold is 9 parts pure gold – that’s 37.5% pure. A 9ct gold ring, blended with alloys such as silver and zinc, is far stronger and more resilient than a 24-carat ring would be.

How much is a one-carat diamond?

It is impossible to answer this question because every diamond is unique. It is valued not just on its weight (carat) but also three other factors:

  • Clarity – a scale ranging from Flawless to Slight Inclusions – tells you how clear or cloudy the diamond is.
  • Colour – while some colours are rare, colourless diamonds (D-F) are the most valuable.
  • Cut – a factor influenced by the skill of the cutter and the type of cut you choose.
  • A one-carat diamond can cost anything from around £2,000+. However, a coloured or very clear and colourless diamond will cost far more.

At PureJewels, we procure diamonds from the world-famous cutting centre in Surat, India (the historic birthplace of natural diamonds). Once they arrive in our workshop, our master jewellers select the brightest to be set into our exclusive collection of engagement rings. How much do you want to spend on a one-carat diamond? If you come to the showroom in person, you can decide how much to spend on the diamond in your engagement ring selecting whether weight, colour or clarity is most important to you. In other words, a one-carat diamond could cost as much or as little as you can afford.

Did you know? The world’s biggest cut diamond – the Star of Africa – is 530 carats, and belongs to the Queen of England.

How big is a one-carat diamond?

This will depend on the cut of your diamond, so it’s essential to go and try some on.

A round, one-carat diamond will measure around half a centimetre; it will not overwhelm your finger, being around a third of a typical finger width.

While a one-carat diamond has an undeniable impact, a cluster of well-cut diamonds can be equally glamorous. You might compliment your one-carat diamond with some additional stones in a halo around it, or add some subtle diamonds on the shoulders of the ring.

The best way to see how big a one-carat diamond will be is to try some on. Why not come in and try on some of our diamonds?