💎 Diamond 4Cs Guide
Understand Cut, Colour, Clarity, and Carat with the real GIA scales. Build a combination to see it explained, or browse the full cut, colour (D–Z), and clarity (FL–I3) scales.
💎 Your 4Cs explained
| C | Grade | What it means |
|---|---|---|
| Cut | Excellent | Maximum brilliance and fire; reflects nearly all light back to the eye. Retailers and AGS often call this tier ‘Ideal’. |
| Colour | F — Colorless | No detectable colour; the rarest and most prized, with icy white brilliance. |
| Clarity | Very Slightly Included 1 | Minor inclusions, difficult to see under 10×; eye-clean. |
| Carat | 1.00 ct | Carat is weight, not size — one carat equals 0.2 grams (200 milligrams). A well-cut one-carat round diamond is about 6.5 mm across. |
The full GIA scales
| Dimension | Grades (best → worst) |
|---|---|
| Cut | Excellent · Very Good · Good · Fair · Poor |
| Colour | D-F Colorless · G-J Near Colorless · K-M Faint · N-R Very Light · S-Z Light |
| Clarity | FL · IF · VVS1 · VVS2 · VS1 · VS2 · SI1 · SI2 · I1 · I2 · I3 |
| Carat | Weight in carats (1 ct = 0.2 g); not a graded scale |
Carat context
- What carat is: Carat is weight, not size — one carat equals 0.2 grams (200 milligrams). A well-cut one-carat round diamond is about 6.5 mm across.
- Points: A carat is divided into 100 points, so a 0.75-carat stone is a ‘75-pointer’ and a half-carat is 50 points.
- Magic sizes: Prices jump at round weights (0.50, 0.75, 1.00, 1.50, 2.00 ct). A 0.90-ct stone can look almost identical to a 1.00-ct but costs noticeably less.
- Size vs weight: Two diamonds of equal carat can look different sizes: a deep cut hides weight below the girdle, while a well-proportioned cut spreads it across the face.
Four letters that set the price
The GIA standardised diamond grading in the mid-20th century, and its four factors are still the language every jeweller speaks. Understanding them is the difference between paying for a grade you can't see and spending where it shows: cut drives sparkle, colour and clarity have wide ‘good enough’ zones, and carat is simply weight — with prices that jump at round numbers.
This guide keeps the real scales — no invented grades — and explains what each level actually looks like. Use it to read a lab report, compare two stones honestly, and decide where your budget buys the most beauty per pound. Always insist on a report from a respected lab such as GIA.
❓ Frequently Asked Questions
What are the 4Cs of a diamond?
Cut, Colour, Clarity, and Carat — the four factors the GIA uses to grade a diamond. Cut is how well the stone is proportioned and returns light, colour is how little tint it has, clarity is how free it is of inclusions, and carat is its weight. Together they determine its beauty and value.
What is the GIA cut scale?
GIA grades cut on five levels: Excellent, Very Good, Good, Fair, and Poor. Cut has the biggest effect on sparkle, so an Excellent or Very Good cut is where most of a stone's brilliance comes from. Many retailers and the AGS label the top tier ‘Ideal’.
How does the diamond colour scale work?
GIA grades colour from D to Z, with D–F colourless, G–J near colourless, K–M faint, N–R very light, and S–Z light. Less colour is rarer and pricier; D is the whitest. Most people can't tell the difference between neighbouring grades face-up, so near-colourless offers strong value.
What do the clarity grades mean?
From best to worst: FL (Flawless), IF (Internally Flawless), VVS1, VVS2, VS1, VS2, SI1, SI2, and I1, I2, I3. It measures inclusions and blemishes under 10× magnification. Many VS and even SI1 stones are ‘eye-clean’, meaning inclusions aren't visible without magnification — another way to get value.
Which of the 4Cs matters most?
Cut, for sparkle — a poorly cut diamond looks dull no matter how good its other grades. After that it's personal: pick the carat weight you want, then balance colour and clarity to stay eye-clean and face-up white within your budget. Always buy a stone with a reputable lab report.