What is a good depth percentage for a round diamond?

For a round brilliant diamond, most gemologists consider a depth percentage between about 59% and 62.5% to be in the ideal range. Stones outside that window can look glassy and dark, or lose their brightness.

Does depth affect how big a diamond looks?

Yes. A shallower stone tends to spread wider face-up so it looks larger for its carat weight, while a very deep stone concentrates more weight below the surface and can appear smaller than its weight suggests.

Is depth the same as depth percentage?

Depth is the raw millimetre measurement, while depth percentage compares that measurement to the stone's diameter. Depth percentage is the more useful figure because it lets you compare proportions across different stone sizes.

What does depth mean in gemstones?

By Jared James · Last updated 21 May 2026

Definition

In gemstone grading, depth is the measurement from the flat top surface of the stone, called the table, down to the lowest point at the bottom, called the culet. It is usually expressed in millimetres and also as a percentage of the stone's width, which is called the depth percentage. Getting this proportion right matters a great deal for how much light a stone returns to the eye; a stone cut too deep or too shallow leaks light out the sides or bottom instead of sending it back up as sparkle.

Frequently asked questions

What is a good depth percentage for a round diamond?: For a round brilliant diamond, most gemologists consider a depth percentage between about 59% and 62.5% to be in the ideal range. Stones outside that window can look glassy and dark, or lose their brightness.
Does depth affect how big a diamond looks?: Yes. A shallower stone tends to spread wider face-up so it looks larger for its carat weight, while a very deep stone concentrates more weight below the surface and can appear smaller than its weight suggests.
Is depth the same as depth percentage?: Depth is the raw millimetre measurement, while depth percentage compares that measurement to the stone's diameter. Depth percentage is the more useful figure because it lets you compare proportions across different stone sizes.

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