The Four Cs
Cut, colour, clarity and carat, and where the money is actually worth spending
Grades Describe. They Do Not Decide.
The Four Cs are cut, colour, clarity and carat. They are genuinely useful, but only when understood properly. A report can tell you the grade. It cannot tell you whether the stone is beautiful to you.
Natural and lab-grown diamonds follow exactly the same grading system, so everything below applies equally to both. What follows is what each of the four actually means, and our honest view on which of them to spend on first.
What Each One Means
Cut
How well the stone is faceted, proportioned and polished. Cut determines how much light the diamond returns, and it is the single most important factor in sparkle. A poorly cut diamond looks dull even with high colour and clarity grades. Do not compromise here.
Colour
Graded D, colourless, through to Z, warm. Once set, G to I offers excellent value with no visible compromise. In yellow or rose gold, even warmer grades look wonderful, and a very white stone suits platinum better.
Clarity
Natural internal features and surface marks, most of them too small to see without magnification. VS clarity is our house recommendation: clean to the eye, without paying for flawless grades nobody can see.
Carat
Weight, not strictly size. Carat has the biggest single effect on price because larger stones are exponentially rarer. A 1.5ct is often nearly double the price of a 1ct of the same quality.
Cut Grades Are Easier on Round Stones
For round brilliant diamonds, cut grades are standardised and easy to compare, so the report does most of the work for you.
For fancy shapes such as oval, pear, cushion, emerald and radiant, the report gives useful information but the stone still has to be judged by eye. Two ovals with identical paperwork can look quite different: one lively and even, the other with a dark bowtie across the centre. This is precisely where a stock-led retailer and a jeweller who sources to your specification part company.
Clarity Scale
For most engagement rings the aim is an eye-clean diamond: no distracting inclusions visible in normal wear.
Shape changes the equation. Open step cuts such as emerald and Asscher hide far less than brilliant cuts, so clarity deserves closer attention there.
Colour Scale
Graded D, colourless, to Z, warm.
Why Two 1ct Diamonds Look Different
Carat is weight, not size
Some stones face up larger than others at the same weight. A shallow stone may look wide but lack life. A deeper stone holds weight underneath the setting where you will never see it.
Shape changes spread
Oval, pear and marquise cuts often look larger than their carat weight suggests, because the weight is distributed across a longer face. Round and cushion read closer to their true weight.
Price rises steeply, not evenly
Because larger rough is exponentially rarer, price jumps at the round numbers. A 0.9ct can cost noticeably less than a 1.0ct while looking almost identical on the hand.
The fifth C: confidence
The unofficial fifth C. It comes from knowing what the stone is, how it has been graded, whether the report is appropriate, whether the price makes sense, and whether the stone suits the design.
Spend Here First
If the budget will not stretch to everything, this is the order we would sacrifice in.
Cut
Sparkle lives here. Never compromise.
VS Clarity
Clean to the eye, without paying for the invisible.
Colour to Suit the Metal
G to I in white; warmer is lovely in gold.
Carat and Visual Spread
Choose what looks right on the hand.
Understanding the Grading Report
Every centre or main diamond should come with an independent grading report appropriate to the stone's type, size and value. A report confirms exact carat weight, cut grade, colour, clarity, fluorescence and measurements, which lets you compare diamonds fairly and insure the ring afterwards. Every individual lab-grown centre stone we supply comes with its own grading report.
Small accent stones do not usually need individual reports. A full eternity ring with many small diamonds is normally specified by quality rather than certified stone by stone.
Four Cs Questions We Are Asked Most
Which of the Four Cs matters most?
Cut, comfortably. It governs how much light the stone returns, and a poorly cut diamond looks lifeless regardless of how good its other grades are. If the budget is tight, sacrifice colour and clarity before cut.
What clarity grade should I buy?
VS1 or VS2 for most rings. Inclusions at that level are invisible without magnification, so paying for VVS or flawless adds cost without changing anything you can see. The exception is emerald and Asscher cuts, where the open facets hide much less and VS1 or better is worth it.
What colour grade should I buy?
G to I is the value sweet spot and looks white to almost every eye once set. If the ring is yellow or rose gold you can go warmer still and it will look beautiful. D to F only really earns its premium in platinum or white gold.
Why do two diamonds of the same carat look different sizes?
Carat is weight, not diameter. A deeper stone hides weight below the setting where you cannot see it, while a shallower one spreads wider. Shape matters too: ovals, pears and marquises face up larger than rounds of the same weight.
Are lab-grown diamonds graded the same way?
Yes. Lab-grown diamonds are chemically, optically and physically identical to mined diamonds and are graded by the same laboratories on the same Four Cs. The only differences are origin and price.
Should I buy just under a carat to save money?
It is one of the easiest savings available. Price jumps at the round weights, so a 0.90ct can cost noticeably less than a 1.00ct while being about two-tenths of a millimetre smaller across. Nobody will ever notice the difference on the hand.
Does fluorescence matter?
Rarely, and it is often overstated. Faint or medium blue fluorescence has no visible effect on most stones and can even improve the look of a warmer diamond. Strong fluorescence occasionally causes a hazy appearance, which is worth checking by eye rather than by report.
The Diamond and Gemstone Guide
The Four Cs in full, plus shapes, natural against lab-grown, fancy colour, coloured gemstones, treatments, durability and grading reports.
Round
Pear
Princess
Emerald
Oval
Asscher
Cushion
Marquise
Radiant
Heart
