What is diamond cut?
By Jared James · Last updated 21 May 2026
Definition
Diamond cut refers to how well a diamond has been shaped, proportioned and faceted to interact with light, and it is widely considered the most important of the four Cs. A well-cut diamond bounces light between its facets and back up through the top, creating the fire, brilliance and scintillation that make it sparkle. Cut also describes the shape of a diamond, such as round brilliant, oval, emerald, pear, princess or cushion, each of which has its own facet arrangement and visual character. GIA grades cut in round brilliants from Excellent down to Poor.
Frequently asked questions
- What is the difference between cut and shape in a diamond?
- Shape is the outline you see from above, such as round, oval or pear. Cut refers to the quality of the faceting and proportions within that shape, which determines how well the stone reflects light. You can have a round diamond in an Excellent cut or a Poor cut.
- Which diamond cut has the most sparkle?
- The round brilliant cut is engineered specifically to maximise light return and has more facets bouncing light than most other shapes. For fancy shapes, radiant and cushion cuts also produce a lot of sparkle.
- Why does cut matter more than other Cs?
- A diamond's colour and clarity are set at birth and cannot be changed, but cut is entirely in the cutter's hands. A poorly cut diamond of excellent colour and clarity will look dull, while a beautifully cut stone of modest colour can be breathtaking.
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