What does the EU ring size number mean?

EU ring sizes (also called ISO ring sizes) represent the inner circumference of the ring in millimeters. For example, EU size 57 fits a finger with an inner circumference of 57 mm. This system is used across most of Europe and internationally.

How is a US ring size different from an EU ring size?

US ring sizes use an arbitrary numerical scale starting near 1 (about 12 mm diameter). EU ring sizes directly state the inner circumference in mm, making them easier to measure and verify with a ruler or string.

How do I measure my ring size at home?

Wrap a thin strip of paper or string around your finger, mark where it overlaps, then measure the length in mm — that is your EU ring size. Divide by π (3.14159) to get the inner diameter in mm.

Is US size 7 the most common ring size?

US size 7 (EU 54–55) is among the most common sizes for women, while US size 10 (EU 62–63) is common for men. However, sizes vary widely, so always measure before ordering.

Are half sizes available in EU ring sizing?

EU ring sizes are continuous millimeter values, so a US half size (e.g., 6.5) simply maps to a specific mm circumference (EU 53). You can request any whole-mm EU size from a jeweler.

Does this converter cover all US ring sizes?

Yes — this tool covers US sizes 1 through 16 in half-step increments (1, 1.5, 2 … 16), which encompasses all standard US ring sizes sold by major jewelers.

US Ring Size to EU Ring Size Converter

Select or enter a US ring size and instantly see the EU equivalent (circumference in mm) from a standard lookup table.

US to EU Ring Size

US Ring Size

Select a US ring size above to see the EU equivalent.

Full US to EU Ring Size Chart

EU size = inner circumference in mm. Diameter = EU ÷ π.

US Size	EU Size (mm circ.)	Inner Diameter (mm)

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Summary

This tool converts US ring sizes to EU ring sizes using the internationally recognized lookup table. EU ring sizes represent the inner circumference of the ring in millimeters, while US sizes use an arbitrary numerical scale. Enter a US size from 1 through 16 (in half-step increments) and the converter instantly returns the EU size along with the corresponding inner diameter in mm.

How it works

Select a US ring size from the dropdown or type it directly.
The tool looks up the standard EU equivalent (circumference in mm) from the conversion table.
The result shows the EU ring size and inner ring diameter.
Copy the result with one click or view the full size chart below.
Use the reference table to find any size at a glance.

Use cases

Shop for rings on European websites when you know your US ring size.
Order a ring as a gift from an international jeweler.
Verify a ring size when converting between US and EU sizing systems.
Find the correct EU size when a ring label only shows a US size.
Compare ring sizes when reading international jewelry catalogs.

Frequently Asked Questions

Last updated: 2026-07-14 · Reviewed by Nham Vu