💍 US / Canada Ring Size to EU / Int'l (circumference mm) Converter
Free online tool to convert US / Canada Ring Size (US) to EU / Int'l (circumference mm) (EU mm). Enter a value and get instant, accurate results.
Enter a value above to see the result
US / Canada Ring Size to EU / Int'l (circumference mm) Conversion Table
| US / Canada Ring Size (US) | EU / Int'l (circumference mm) (EU mm) |
|---|---|
| 5 US | 49.260173 EU mm |
| 6 US | 51.873978 EU mm |
| 7 US | 54.487783 EU mm |
| 8 US | 57.101588 EU mm |
| 9 US | 59.715393 EU mm |
| 10 US | 62.329198 EU mm |
Conversion Formula
Ring size conversion formulas (approximate): EU (mm circ.) = diameter_mm × π diameter_mm = 11.52 + US × 0.832 (±0.1 mm) JP size ≈ US × 2 − 1 (exact for integer sizes) Common size reference: US 5 = EU 49.3 = JP 9 = 15.7 mm diameter US 6 = EU 51.8 = JP 11 = 16.5 mm diameter US 7 = EU 54.4 = JP 13 = 17.3 mm diameter US 8 = EU 57.0 = JP 15 = 18.2 mm diameter US 9 = EU 59.5 = JP 17 = 18.9 mm diameter US 10 = EU 62.1 = JP 19 = 19.8 mm diameter UK ring sizes use letters (F–Z) — UK A ≈ US 2.5, adding ~0.5 US per letter. UK F = US 3 • UK J = US 5 • UK N = US 7 • UK T = US 10
About US / Canada Ring Size to EU / Int'l (circumference mm) Conversions
The US to EU mm ring size converter handles the differences between international sizing systems. Enter a size below for an instant result.
This conversion uses a non-linear (reciprocal) relationship, so a simple multiplication factor does not apply. The formula section below explains the method, and the reference table shows common converted values.
This page includes a reference table of common US / Canada Ring Size values pre-converted to EU / Int'l (circumference mm), the conversion formula, and frequently asked questions. All values use internationally recognized conversion standards.
Note on ring sizes: Conversions use a linear approximation (±0.1 mm). Minor variations exist between jewelers and countries. For important purchases, have your finger professionally sized using physical sizing rings.
Frequently Asked Questions
How do I convert US / Canada Ring Size to EU / Int'l (circumference mm)?
This conversion is non-linear. Use the calculator above for accurate results, or refer to the formula section on this page.
How many EU / Int'l (circumference mm) are in 1 US / Canada Ring Size?
The relationship between US / Canada Ring Size and EU / Int'l (circumference mm) is non-linear. Use the calculator above or the reference table on this page for specific values.
Is US / Canada Ring Size larger or smaller than EU / Int'l (circumference mm)?
The size relationship between US / Canada Ring Size and EU / Int'l (circumference mm) depends on the input value because this conversion is non-linear (reciprocal).
When would I use EU / Int'l (circumference mm) instead of US / Canada Ring Size?
Use EU mm sizing when the jeweler or retailer you are purchasing from uses that system. For important purchases, have your finger sized professionally — ring size can vary with temperature and time of day.
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All conversion results are provided for general informational purposes only. Our formulas use internationally recognized conversion factors; however, rounding may affect precision. Do not rely on these results for professional, medical, legal, or engineering decisions without independent verification. Read our full disclaimer.