Diamond grading scales
A grade is a defined position on a published scale, not an opinion. The scope limits matter as much as the grades: a cutgrade is issued only for round brilliants, so an oval or a cushion has no cut grade at all — a fact that surprises most buyers looking for “Excellent” on a fancy shape.
4 entries
All cited
SortedA–Z
| Name | Scale range | Number of grades | What it measures | Applies to | Viewing condition |
|---|---|---|---|---|---|
| Diamond carat weight (GIA) | — | — | Weight, not size. A metric carat is defined as 200 milligrams, subdivided into… | Diamonds and, as a unit of weight, gemstones generally. | Measured on a calibrated scale, not assessed by eye. |
| Diamond clarity (GIA) | Flawless (FL) to Included (I3) | 11 | The number, size, relief, nature and location of clarity characteristics — inc… | Diamonds. | 10x magnification. Every diamond is evaluated under 10x and assigned a grade. |
| Diamond colour (GIA D-to-Z) | D (colourless) to Z (light) | — | Absence of colour. Stones are compared against masterstones of established gra… | Diamonds in the normal colour range. Diamonds occur from colourless through ye… | Controlled lighting, compared side by side against masterstones. |
| Diamond cut (GIA) | Excellent to Poor | — | How the diamond interacts with light, plus design and craftsmanship. Face-up a… | STANDARD ROUND BRILLIANTS ONLY. Cut grades are given only to round brilliants … | Face-up appearance, plus design and craftsmanship. |
Showing all 4Every figure traces to a named source with a pinpoint locator. Values we could not source are left blank rather than estimated.