Every diamond is graded on four qualities, known as the 4Cs: cut, colour, clarity and carat weight. Together they decide how a diamond looks and what it costs. Here is what each means, in plain language, and how to balance them.
1. Cut: the one that matters most
Cut is how well a diamond's facets are proportioned and finished, and it decides how much light the stone returns as brilliance (white light), fire (flashes of colour) and scintillation (sparkle). A well-cut diamond looks bright and lively; a poorly cut one looks dull or dark, whatever its other grades. For round brilliants, look for Excellent (GIA) or Ideal grades. Fancy shapes have no single cut grade, so look at the stone itself and at its polish and symmetry.
2. Colour: how white the diamond is
White diamonds are graded from D (colourless) to Z (light yellow or brown). D to F are colourless, G to J near-colourless. Differences between neighbouring grades are very hard to see once a diamond is set. Many people choose G or H for the best balance, and yellow or rose gold settings are kind to warmer grades. Diamonds with strong, attractive colour, such as yellow, pink or blue, are graded separately as fancy colours.
3. Clarity: how clean the diamond is
Clarity grades the tiny natural features inside or on the surface of a diamond, called inclusions and blemishes, from Flawless (FL) through VVS and VS to SI and I. Most are invisible without magnification. What matters is that the diamond is "eye-clean": nothing visible from normal viewing distance. In brilliant shapes, VS2 or SI1 is often eye-clean; step cuts such as emerald and asscher show more, so many people choose VS or better.
4. Carat: the weight, not the size
Carat is a measure of weight: one carat is 0.2 grams. Two diamonds of the same weight can look different in size depending on their cut and shape; ovals, pears and marquise diamonds look larger for their weight. Prices rise steeply at whole and half carats, so a 0.9 carat diamond can be a smart choice. Read more in understanding carat weight.
How to balance the 4Cs
- Choose a shape you love.
- Put cut first.
- Choose the colour and clarity you cannot see a difference above.
- Let the remaining budget decide the carat weight.
The fifth C: certificate
Always choose a diamond graded by an independent laboratory such as GIA or IGI. The report confirms the 4Cs and whether the diamond is natural or lab-grown. Every centre diamond in our diamond search is certified, and you can filter by shape, carat, colour, clarity and cut, natural or lab-grown.