Measurement Guide
Ring Size Chart in Centimetres (cm)
If you measured your finger with a string and a standard centimetre ruler, use this chart to convert circumferences from 4.5 cm to 9 cm into your precise ring size.
Centimetres to Ring Size
Converting cm to mm is simple: just multiply by 10 (e.g., 5.5 cm = 55 mm). Our table below handles the direct cm conversion for you.
| Circumference (cm) | Circumference (mm) | US / Canada | UK / Australia | EU / ISO |
|---|---|---|---|---|
| 4.5 cm | 45 mm | 3.25 | G | 45 |
| 5.0 cm | 50 mm | 5.25 | K 1/2 | 50 |
| 5.5 cm | 55 mm | 7.25 | O | 55 |
| 6.0 cm | 60 mm | 9 | S | 60 |
| 6.5 cm | 65 mm | 11 | W | 65 |
| 7.0 cm | 70 mm | 13 | Z+1 | 70 |
| 8.0 cm | 80 mm | 16 | Z+6 | 80 |
| 9.0 cm | 90 mm | - | - | 90 |
Written by Evelyn Moore
Evelyn is a certified GIA Gemologist with over a decade of experience in fine jewelry sizing and design. She ensures all conversion charts and measuring advice strictly adhere to ISO 8653 standards.