Diamond 4Cs cheat sheet
The grading scales on one page, with what we look for.
Laboratories such as GIA and IGI grade every diamond on cut, colour, clarity and carat. Use this table as a quick reference when you read a grading report, then see the full four Cs guide for the detail.
From the CTJ Jewellery team, led by founder Greg Ward
| Scale | What it measures | What we look for | |
|---|---|---|---|
| Cut | Excellent · Very good · Good · Fair · Poor | The proportions, symmetry and polish that decide brightness, fire and sparkle. | Excellent. It does more for appearance than any other grade. |
| Colour | D E F · G H · I J · K L M · N to Z | The absence of colour. D is completely colourless. | Match to the metal. White metals show colour most, yellow and rose gold warm it. |
| Clarity | FL · IF · VVS1 VVS2 · VS1 VS2 · SI1 SI2 · I1 I2 I3 | Inclusions and blemishes seen under 10× magnification. | Eye-clean. Beyond that you pay for clarity you can’t see. |
| Carat | 0.2 grams per carat | Weight, not size. Jewellery with several diamonds is quoted in TDW. | Just under a round weight, such as 0.95ct, looks the same as 1.00ct. |
Sources and further reading
How to read a grading report in five steps
- Check the laboratory and report number, and match it to the girdle inscription.
- Confirm origin: natural or laboratory-grown.
- Read shape, measurements and carat weight.
- Read colour, clarity and, for rounds, cut, polish and symmetry.
- Look at the clarity plot and fluorescence, then compare the diamond in person.