The 4Cs of Diamonds Explained: How to Buy in 2026
Mastering the 4Cs of diamonds — cut, colour, clarity and carat — is the key to buying a diamond with confidence in 2026. These four factors determine a diamond's beauty, quality and price. This guide explains each C in simple terms, how to balance them, and how they shape the diamond you choose.
See the 4Cs in action with Kohinoor Gems' fine lab-grown diamonds — VVS1 clarity, FG colour, starting around $1,799 USD with free shipping over $250.
The 4Cs: An Overview
| C | What It Measures | Affects |
|---|---|---|
| Cut | Proportions & light return | Brilliance & sparkle |
| Colour | Lack of colour | Whiteness & brightness |
| Clarity | Inclusions & blemishes | Cleanliness |
| Carat | Weight | Size & presence |
Cut: The Most Important C
Cut describes how well a diamond's proportions interact with light. A well-cut diamond reflects light back to the eye with maximum brightness and fire. Cut grades range from Ideal/Excellent to Poor — and it's the one C you should never compromise on, because it drives beauty more than any other factor.
Colour: How White Is the Diamond?
Colour measures how colourless a diamond is, graded from D (colourless) to Z (light yellow). Colourless diamonds (D–F) look brightest; near-colourless stones (G–H) offer excellent value while remaining white to the eye. FG colour — the sweet spot at Kohinoor Gems — delivers near-colourless brilliance.
| Grade | Description |
|---|---|
| D–F | Colourless (rarest, brightest) |
| G–H | Near-colourless (great value) |
| I–J | Slightly tinted (budget-friendly) |
| K–Z | Visible colour |
Clarity: How Clean Is the Diamond?
Clarity grades the presence of internal inclusions and surface blemishes, from Flawless (FL) to Included (I). Most inclusions are invisible to the naked eye. VVS1 – VS clarity offers a perfectly clean appearance at a sensible price — the quality Kohinoor Gems recommends.
| Grade | Meaning |
|---|---|
| FL / IF | Flawless / internally flawless |
| VVS1–VVS2 | Very very slightly included (invisible) |
| VS1–VS2 | Very slightly included (invisible) |
| SI1–SI2 | Slightly included (usually invisible) |
| I1–I3 | Included (visible) |
Carat: The Size Factor
Carat is simply the weight of the diamond — 1 carat = 0.2 grams. Larger carats cost more per carat as size increases. Carat drives visual presence, but a smaller, well-cut diamond can out-sparkle a larger, poorly cut one.
How to Balance the 4Cs
- Prioritise cut for maximum sparkle.
- Choose FG colour for brightness without premium cost.
- Buy VVS1–VS clarity — inclusions are invisible anyway.
- Spend on carat only after securing a great cut.
Lab-Grown vs Natural on the 4Cs
Lab-grown diamonds are graded on the identical 4Cs scale as natural diamonds. Kohinoor Gems selects lab-grown diamonds with VVS1 clarity and FG colour — a combination that delivers premium quality at a more accessible price.
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Your Diamond Buying Checklist
- Choose a shape and style you love.
- Prioritise cut for brilliance.
- Target FG colour.
- Target VVS1–VS clarity.
- Set a carat size and budget.
- Buy from a transparent, quality jeweller.