The 4Cs — Cut, Colour, Clarity and Carat — are the four qualities that define a diamond and set its price. Cut governs how brilliantly the stone returns light; Colour measures how close it comes to truly colourless; Clarity records the tiny natural marks formed inside it; and Carat is its weight. Of the four, Cut has the greatest effect on how a diamond actually looks. Learn how they balance one another and you can buy a more beautiful stone for less — without ever compromising on the piece.
The four grades behind every diamond, at a glance.
Cut — the source of sparkle
Cut is the only one of the 4Cs shaped entirely by human hands, and it matters most. It describes how precisely a diamond's facets have been proportioned and polished — not its shape. When the angles are right, light enters through the top, reflects from one facet to the next, and returns to your eye as brilliance and fire. When they are wrong, that light leaks out of the sides or bottom and the stone looks lifeless, however large or flawless it may be.
Laboratories grade cut from Excellent down to Poor for round brilliant diamonds. Our guidance is simple: buy the best cut you can afford. An Excellent-cut diamond of a modest colour and clarity will almost always outshine a poorly cut stone with superior grades on paper.
Colour — how white the diamond is
Diamond colour is graded on a scale from D to Z, where D is completely colourless and Z carries a light yellow or brown tint. The differences are subtle: from D through F a diamond is colourless, and from G through J it is near-colourless, appearing white to the eye once set. Because the scale measures the absence of colour, higher letters command higher prices — yet most of that premium is invisible once the stone is mounted, especially in yellow or rose gold, which gently warms the metal around it.
For a bright white appearance at sensible value, G to H is the enduring sweet spot. Reserve D to F for platinum and white-gold settings where you want the coolest possible white.
Clarity — the diamond's natural fingerprint
Clarity records the tiny inclusions and surface marks that form as a diamond crystallises deep in the Earth. These are entirely natural and, in most stones, completely invisible without magnification. The scale runs from Flawless (FL) through Very Very Slightly Included (VVS), Very Slightly Included (VS) and Slightly Included (SI), down to Included (I), where marks may be visible to the naked eye.
The phrase to remember is eye-clean: a diamond in which no inclusion is visible to an unaided eye at normal viewing distance. Many VS2 and SI1 stones are perfectly eye-clean, which is why they offer some of the best value on the scale. You are paying for beauty, not for perfection under a microscope.
Carat — weight, not size
Carat is a measure of weight, not dimensions: one carat equals 0.20 grams, divided into 100 points, so a 0.50ct diamond is described as fifty points. Because larger crystals are rarer, price rises steeply — and it jumps sharply at the round-number weights buyers ask for. A 1.00ct diamond can cost noticeably more than a 0.90ct stone that looks almost identical face-up. Choosing a weight just below a milestone, such as 0.90ct or 1.90ct, is one of the quietest ways to buy well.
How the 4Cs work together
No single C tells the whole story. A diamond is beautiful when the four are balanced for how it will be worn and seen. Prioritise Cut first, because it drives the sparkle everyone notices; then choose a near-colourless grade, an eye-clean clarity, and the carat weight that suits the setting and the hand. Judged this way — as a whole, never by one number alone — the 4Cs become a tool for buying a more radiant diamond, not a taller price.