⚠ Important: For 100% Ring Size Accuracy, visit your local jeweler for an in-person measurement. All tools on this site are estimates only.
International Conversion

Ring Size Conversion

Convert between US, UK, EU, Japanese, Swiss, and mm ring sizes — the complete international ring size conversion reference.

Converting between international ring sizing systems is essential when shopping globally. This page is your complete reference for ring size conversion — covering every major system used worldwide.

Full Ring Size Conversion Table

US / CanadaUK / IRE / AUSEU / FrenchJapan / ChinaSwissDiameter (mm)Circumference (mm)
3F444414.144.2
3.5G455514.545.6
4H46.576.514.946.8
4.5I488815.348.0
5J499915.749.3
5.5K50.51110.516.150.6
6L51.51211.516.551.9
6.5M53131316.953.2
7N54141417.354.4
7.5O55.51615.517.755.7
8P57171718.257.2
8.5Q58181818.558.2
9R59191918.959.3
9.5S61212119.461.0
10T62222219.862.2
10.5U63.52423.520.263.5
11V65252520.765.0
11.5W66262621.166.2
12X67.52827.521.567.5
12.5Y68.52928.521.968.8
13Z70303022.370.1
14Z+271313122.771.3

Quick Conversion Reference

US to UK Conversions

  • US 5 = UK J  ·  US 5.5 = UK K  ·  US 6 = UK L
  • US 6.5 = UK M  ·  US 7 = UK N  ·  US 7.5 = UK O
  • US 8 = UK P  ·  US 8.5 = UK Q  ·  US 9 = UK R
  • US 9.5 = UK S  ·  US 10 = UK T  ·  US 10.5 = UK U
  • US 11 = UK V  ·  US 12 = UK X  ·  US 13 = UK Z

US to EU Conversions

  • US 5 = EU 49  ·  US 6 = EU 51.5  ·  US 7 = EU 54
  • US 8 = EU 57  ·  US 9 = EU 59  ·  US 10 = EU 62
  • US 11 = EU 65  ·  US 12 = EU 67.5  ·  US 13 = EU 70

UK to EU Conversions

  • UK J = EU 49  ·  UK L = EU 51.5  ·  UK N = EU 54
  • UK P = EU 57  ·  UK R = EU 59  ·  UK T = EU 62
  • UK V = EU 65  ·  UK X = EU 67.5  ·  UK Z = EU 70

Why Ring Sizes Don't Convert Directly

There is no simple mathematical formula between US numbers and UK letters, or between US numbers and EU sizes. Each system was developed independently with different base references and increment sizes. The only reliable conversion method is a reference table like the one above, or using mm diameter/circumference as a universal intermediary.

Universal tip: When working with international jewellers, always communicate in millimetre diameter or circumference. This bypasses all conversion ambiguity. Saying "my finger is 54mm circumference" or "I need a ring with 17.3mm inside diameter" is understood everywhere.