Ruby Size Chart (Round)
Carat to mm size chart for round-cut Ruby, from 0.25ct to 40ct. The chart is interactive, meaning you can click on any stone to view it directly in the size simulator.
Gem sizes are shown in actual, real-world size, provided your device screen size is in diagonal. If this is not correct, change it here:
Gem sizes are shown in actual, real-world size, provided your device screen size is in diagonal. If this is not correct, change it here:
Actual size is set for screen
Gemstone:
Shape:
Ruby Size Chart (Round Cut)
0.25ct
3.77×3.77 mm
3.77×3.77 mm
0.5ct
4.75×4.75 mm
4.75×4.75 mm
0.75ct
5.43×5.43 mm
5.43×5.43 mm
1ct
5.98×5.98 mm
5.98×5.98 mm
1.25ct
6.44×6.44 mm
6.44×6.44 mm
1.5ct
6.84×6.84 mm
6.84×6.84 mm
1.75ct
7.2×7.2 mm
7.2×7.2 mm
2ct
7.53×7.53 mm
7.53×7.53 mm
2.5ct
8.11×8.11 mm
8.11×8.11 mm
3ct
8.62×8.62 mm
8.62×8.62 mm
3.5ct
9.08×9.08 mm
9.08×9.08 mm
4ct
9.49×9.49 mm
9.49×9.49 mm
4.5ct
9.87×9.87 mm
9.87×9.87 mm
5ct
10.22×10.22 mm
10.22×10.22 mm
5.5ct
10.55×10.55 mm
10.55×10.55 mm
6ct
10.86×10.86 mm
10.86×10.86 mm
6.5ct
11.16×11.16 mm
11.16×11.16 mm
7ct
11.44×11.44 mm
11.44×11.44 mm
7.5ct
11.7×11.7 mm
11.7×11.7 mm
8ct
11.96×11.96 mm
11.96×11.96 mm
8.5ct
12.2×12.2 mm
12.2×12.2 mm
9ct
12.44×12.44 mm
12.44×12.44 mm
9.5ct
12.66×12.66 mm
12.66×12.66 mm
10ct
12.88×12.88 mm
12.88×12.88 mm
11ct
13.3×13.3 mm
13.3×13.3 mm
12ct
13.69×13.69 mm
13.69×13.69 mm
13ct
14.06×14.06 mm
14.06×14.06 mm
14ct
14.41×14.41 mm
14.41×14.41 mm
15ct
14.74×14.74 mm
14.74×14.74 mm
16ct
15.06×15.06 mm
15.06×15.06 mm
17ct
15.37×15.37 mm
15.37×15.37 mm
18ct
15.67×15.67 mm
15.67×15.67 mm
19ct
15.95×15.95 mm
15.95×15.95 mm
20ct
16.23×16.23 mm
16.23×16.23 mm
22ct
16.75×16.75 mm
16.75×16.75 mm
24ct
17.24×17.24 mm
17.24×17.24 mm
26ct
17.71×17.71 mm
17.71×17.71 mm
28ct
18.15×18.15 mm
18.15×18.15 mm
30ct
18.58×18.58 mm
18.58×18.58 mm
33ct
19.18×19.18 mm
19.18×19.18 mm
36ct
19.74×19.74 mm
19.74×19.74 mm
40ct
20.45×20.45 mm
20.45×20.45 mm
Length-to-width ratio: 1, Color:
Download Chart
Note: If you want to cut out the shapes and try them on your finger, print out the PDF chart. The image (png) chart will not print at actual size.
Carat-to-MM Conversion Table
Use this conversion table to quickly convert round-cut Ruby carat weights to their approximate millimeter (mm) sizes:
| Carat Weight | MM Size |
|---|---|
| 0.25 ct | 3.77×3.77 mm |
| 0.5 ct | 4.75×4.75 mm |
| 0.75 ct | 5.43×5.43 mm |
| 1 ct | 5.98×5.98 mm |
| 1.25 ct | 6.44×6.44 mm |
| 1.5 ct | 6.84×6.84 mm |
| 1.75 ct | 7.2×7.2 mm |
| 2 ct | 7.53×7.53 mm |
| 2.5 ct | 8.11×8.11 mm |
| 3 ct | 8.62×8.62 mm |
| 3.5 ct | 9.08×9.08 mm |
| 4 ct | 9.49×9.49 mm |
| 4.5 ct | 9.87×9.87 mm |
| 5 ct | 10.22×10.22 mm |
| 5.5 ct | 10.55×10.55 mm |
| 6 ct | 10.86×10.86 mm |
| 6.5 ct | 11.16×11.16 mm |
| 7 ct | 11.44×11.44 mm |
| 7.5 ct | 11.7×11.7 mm |
| 8 ct | 11.96×11.96 mm |
| 8.5 ct | 12.2×12.2 mm |
| Carat Weight | MM Size |
|---|---|
| 9 ct | 12.44×12.44 mm |
| 9.5 ct | 12.66×12.66 mm |
| 10 ct | 12.88×12.88 mm |
| 11 ct | 13.3×13.3 mm |
| 12 ct | 13.69×13.69 mm |
| 13 ct | 14.06×14.06 mm |
| 14 ct | 14.41×14.41 mm |
| 15 ct | 14.74×14.74 mm |
| 16 ct | 15.06×15.06 mm |
| 17 ct | 15.37×15.37 mm |
| 18 ct | 15.67×15.67 mm |
| 19 ct | 15.95×15.95 mm |
| 20 ct | 16.23×16.23 mm |
| 22 ct | 16.75×16.75 mm |
| 24 ct | 17.24×17.24 mm |
| 26 ct | 17.71×17.71 mm |
| 28 ct | 18.15×18.15 mm |
| 30 ct | 18.58×18.58 mm |
| 33 ct | 19.18×19.18 mm |
| 36 ct | 19.74×19.74 mm |
| 40 ct | 20.45×20.45 mm |