Buying
How to read a diamond grading report
By the Encore Luxe specialists · Updated October 2026
A diamond grading report looks technical, and it is. It is also one of the most useful documents in jewellery, because it describes a stone in a consistent language that any jeweller understands. This guide explains how to read one, starting with the four Cs.
Who issues reports
Grading reports are issued by independent gemmological laboratories. The best known is the Gemological Institute of America (GIA), which developed the colour and clarity scales most widely used today. A report records the laboratory's assessment on the day the stone was examined. It is not an appraisal and it does not describe the setting.
Carat weight
Carat is a unit of weight, not size: one carat is 0.2 grams. Reports give it to two decimal places, for example 0.52 ct. Two diamonds of the same weight can look different in size depending on their cut and proportions.
Colour
White diamonds are graded on a scale from D (colourless) to Z (light yellow or brown).
| Grades | Description |
|---|---|
| D, E, F | Colourless |
| G, H, I, J | Near colourless |
| K, L, M | Faint |
| N to R | Very light |
| S to Z | Light |
The differences between neighbouring grades are subtle and usually visible only when stones are compared side by side under controlled light. The diamond in the Tiffany Setting engagement ring in our shop is described as F colour, in the colourless range.
Fancy coloured diamonds
Diamonds with strong natural colour are graded differently. The report describes the hue (yellow, pink, blue and so on) and the intensity of the colour, using GIA's terms Faint, Very Light, Light, Fancy Light, Fancy, Fancy Intense and Fancy Vivid, with Fancy Dark and Fancy Deep describing strong colour with a darker tone. A report will also state whether the colour is natural. The Tiffany Fancy Intense Yellow diamond ring is graded Fancy Intense Yellow.
Clarity
Clarity describes inclusions (internal features) and blemishes (surface features), judged under ten-times magnification.
| Grade | Meaning |
|---|---|
| FL | Flawless |
| IF | Internally flawless |
| VVS1, VVS2 | Very, very slightly included |
| VS1, VS2 | Very slightly included |
| SI1, SI2 | Slightly included |
| I1, I2, I3 | Included |
Most inclusions in the VS range and above are invisible to the naked eye. A report usually includes a plotted diagram showing where the main inclusions lie.
Cut
For round brilliant diamonds, GIA reports grade cut from Excellent to Poor, considering proportions, symmetry and polish. Cut has the greatest effect on how a diamond returns light, its brightness, fire and sparkle. For other shapes, the report describes the shape and measurements and grades polish and symmetry.
Other details
Measurements give the stone's dimensions in millimetres. Fluorescence describes whether the diamond glows under ultraviolet light, and how strongly; faint fluorescence is common and rarely visible in normal light. Comments note anything else of interest. Inscription records any number or text laser-inscribed on the girdle.
Matching a report to a stone
A report is only useful if it belongs to the stone in front of you. Where the report number is inscribed on the girdle, a jeweller can read it under magnification and compare it with the report. Laboratories also let you check a report number online. Where there is no inscription, measurements, weight and the plotted inclusions help to match stone and report.
Reports and house certificates
Houses such as Tiffany & Co. and Cartier may also issue their own documents describing their jewellery. These are useful, and like all paperwork they support rather than replace examination of the piece itself. See our guide to box and papers.
Browse fine jewellery in the shop, or read our guides to Tiffany & Co., De Beers and caring for fine jewellery.
Questions we’re often asked
- What are the 4Cs of a diamond?
Carat weight, colour, clarity and cut. Together they describe a diamond's size, how colourless it is, how free it is of inclusions and how well it has been cut to return light.
- What does F VS1 mean?
F is a colour grade in the colourless range of the D-to-Z scale. VS1 is a clarity grade meaning very slightly included, with inclusions that are difficult to see under ten-times magnification.
- What does Fancy Intense Yellow mean?
Coloured diamonds are graded on a separate scale that describes the strength of their colour. Fancy Intense is one of the stronger grades, above Fancy Light and Fancy. Fancy Vivid describes the most saturated colour, while Fancy Dark and Fancy Deep describe strong colour with a darker tone.
- Is a grading report the same as an authenticity certificate?
No. A grading report describes a stone. It does not describe the setting, confirm who made the jewellery or prove that the report belongs to the stone in front of you without checking.