Diamond size chart for all shapes: carat to mm

By HeyGema™ · Updated

In short

Find your shape in the first column and your weight along the top. A 1 carat round is 6.5 mm, a 1 carat oval 8.0 x 5.5 mm and a 1 carat emerald cut 7.0 x 5.0 mm.

Round
6.5 mm
Oval
8.0 x 5.5 mm
Cushion
5.6 x 5.6 mm
Princess
5.5 x 5.5 mm
Emerald cut
7.0 x 5.0 mm
Asscher
5.5 x 5.5 mm
Radiant
6.5 x 5.0 mm
Pear
8.5 x 5.5 mm
Marquise
10.4 x 5.2 mm
Heart
6.5 x 6.5 mm
Trillion
7.0 x 7.0 mm
Baguette
8.0 x 4.0 mm
= 2 mm in every picture above
A 1 carat diamond in 12 shapes, to one scale.

Carat to mm for every diamond shape

Length x width of a well-cut diamond at each weight. Round diamonds show one number, their diameter. Each cell links to the page for that shape and weight.

Shape0.5 ct0.75 ct1 ct1.5 ct2 ct2.5 ct3 ct4 ct5 ct
Round5.15.96.57.48.18.89.310.211.0
Oval6.3 x 4.47.3 x 5.08.0 x 5.59.2 x 6.310.1 x 6.910.9 x 7.511.5 x 7.912.7 x 8.713.7 x 9.4
Cushion4.4 x 4.45.1 x 5.15.6 x 5.66.4 x 6.47.1 x 7.17.6 x 7.68.1 x 8.18.9 x 8.99.6 x 9.6
Princess4.4 x 4.45.0 x 5.05.5 x 5.56.3 x 6.36.9 x 6.97.5 x 7.57.9 x 7.98.7 x 8.79.4 x 9.4
Emerald cut5.6 x 4.06.4 x 4.57.0 x 5.08.0 x 5.78.8 x 6.39.5 x 6.810.1 x 7.211.1 x 7.912.0 x 8.5
Asscher4.4 x 4.45.0 x 5.05.5 x 5.56.3 x 6.36.9 x 6.97.5 x 7.57.9 x 7.98.7 x 8.79.4 x 9.4
Radiant5.2 x 4.05.9 x 4.56.5 x 5.07.4 x 5.78.2 x 6.38.8 x 6.89.4 x 7.210.3 x 7.911.1 x 8.5
Pear6.7 x 4.47.7 x 5.08.5 x 5.59.7 x 6.310.7 x 6.911.5 x 7.512.3 x 7.913.5 x 8.714.5 x 9.4
Marquise8.3 x 4.19.4 x 4.710.4 x 5.211.9 x 6.013.1 x 6.614.1 x 7.115.0 x 7.516.5 x 8.317.8 x 8.9
Heart5.2 x 5.25.9 x 5.96.5 x 6.57.4 x 7.48.2 x 8.28.8 x 8.89.4 x 9.410.3 x 10.311.1 x 11.1
Trillion5.6 x 5.66.4 x 6.47.0 x 7.08.0 x 8.08.8 x 8.89.5 x 9.510.1 x 10.111.1 x 11.112.0 x 12.0
Baguette6.3 x 3.27.3 x 3.68.0 x 4.09.2 x 4.610.1 x 5.010.9 x 5.411.5 x 5.812.7 x 6.313.7 x 6.8

All sizes in mm. Scroll sideways to see every weight.

How to read the chart

Pick the shape you like, then the weight you are considering, and read the length and width. For a long shape such as an oval or an emerald cut, the length runs along the finger and the width is what shows across it. Two stones of the same weight can differ by more than a millimeter in width, so check the millimeters, not only the carats.

Questions

At the same weight, the shapes with the most face-up area look biggest. In our chart that is Marquise, then Oval and Emerald cut. See which shapes look biggest.
Yes. Lab grown and mined diamonds have the same density, so the same weight measures the same. See the lab grown diamond size chart.

More size charts