US ring sizes are decimal numbers and EU ring sizes are based on inner circumference in millimeters, so there is no simple formula to convert between them without a reference table. When you are shopping a European brand, a luxury jeweler like Cartier or Van Cleef, or any international retailer that lists EU sizes, knowing your equivalent EU number saves you from guessing.
This guide gives you a complete US to EU ring size chart, explains how the EU system works, and covers what to do when your size falls between EU numbers.
US to EU Ring Size Conversion Chart
| US size | EU size | UK size | Inner diameter (mm) | Inner circumference (mm) |
|---|---|---|---|---|
| 3 | 44 | F | 14.1 | 44.2 |
| 3.5 | 45.5 | G | 14.5 | 45.5 |
| 4 | 46.8 | H | 14.9 | 46.8 |
| 4.5 | 48 | I½ | 15.3 | 48.0 |
| 5 | 49.3 | J½ | 15.7 | 49.3 |
| 5.5 | 50.6 | K½ | 16.1 | 50.6 |
| 6 | 51.9 | L½ | 16.5 | 51.9 |
| 6.5 | 53.1 | M½ | 16.9 | 53.1 |
| 7 | 54.4 | N½ | 17.3 | 54.4 |
| 7.5 | 55.7 | O½ | 17.7 | 55.7 |
| 8 | 57.2 | P½ | 18.2 | 57.2 |
| 8.5 | 58.5 | Q½ | 18.6 | 58.5 |
| 9 | 59.7 | R½ | 19.0 | 59.7 |
| 9.5 | 61 | S½ | 19.4 | 61.0 |
| 10 | 62.2 | T½ | 19.8 | 62.2 |
| 10.5 | 63.5 | U½ | 20.2 | 63.5 |
| 11 | 64.8 | V½ | 20.6 | 64.8 |
| 12 | 67.2 | X½ | 21.4 | 67.2 |
| 13 | 69.7 | Z | 22.2 | 69.7 |
How the EU Ring Size System Works
EU ring sizes are based directly on the inner circumference of the ring in millimeters. A ring labeled EU 52 has an inner circumference of approximately 52mm, which means the number carries real dimensional meaning. This is unlike the US system, where the numbers are an arbitrary scale, or the UK system, which uses letters.
Because EU sizes are circumference values, they increase continuously and can include decimals. When jewelers round to whole numbers, sizes like 49.3 may be listed as 49 or 50. Always check whether a brand rounds up or down and read the fine print in their size guide.
Shopping European Brands from the US
If you know your US size and want to buy from a European brand, the most reliable path is: find your US size in the left column, read across to the EU size, then find that number on the brand's size chart. If the brand only shows whole EU numbers, round to the nearest one.
For specific luxury brand sizing like Cartier, sizes tend to follow the same EU system. See our dedicated Cartier ring size guide for a brand-specific chart. For Indian sizing used by some European-influenced brands, see US to India ring size conversion.
Converting EU to US
To convert in the reverse direction, find your EU size in the second column and read across to the US column. EU 52 is approximately US 6, EU 54 is US 7, and EU 57 is US 8.
The millimeter column is your safest reference when sizes do not align perfectly. Any jeweler worldwide can work with your inner diameter in mm, so keep that number as your primary measurement. To measure your finger and get your mm size, use our ring size calculator or follow the steps in our guide on how to measure ring size at home.
FAQ
What is US size 7 in EU ring sizing?
US size 7 is approximately EU size 54 to 54.4, with an inner circumference of about 54.4mm and a diameter of 17.3mm.
What is EU 52 in US ring size?
EU 52 corresponds to approximately US size 6, with an inner diameter of about 16.5mm.
Is EU ring size the same as French ring size?
Yes. French and most other continental European countries use the same circumference-based system, sometimes called the ISO or EU standard.
What is EU size 54 in US?
EU 54 is approximately US size 7, UK N½, with an inner diameter of about 17.3mm.
