What does an EU ring size number mean?

An EU ring size is the inner circumference of the ring in millimeters. EU size 52, for example, means the inside of the ring measures 52 mm around.

How do I find my EU ring size to convert it?

Check inside an existing ring for a stamped number, or wrap a strip of paper around your finger, mark the overlap, and measure that length in millimeters with a ruler.

Why do UK ring sizes use letters instead of numbers?

UK ring sizing is a historic system that assigns a letter, A through Z and beyond, to each step in circumference. Half sizes are shown with a half symbol, such as L½.

What if my EU size falls between two UK sizes on the chart?

The tool snaps to the closest UK letter and shows how many millimeters off the match is, so you can decide whether to size up or down.

Is there an exact formula between EU and UK ring sizes?

Not a single official one. Jewelry trade charts are built from measured circumference tables, and this converter uses the commonly referenced EU-to-UK chart, so results can differ from another chart by a fraction of a millimeter.

EU Ring Size to UK Ring Size Converter

Name: EU Ring Size to UK Ring Size Converter
Availability: InStock
Author: Nham Vu

Enter an EU ring size (mm circumference) to instantly find the equivalent UK letter size, with diameter and a full reference chart.

EU to UK Ring Size

EU Ring Size (mm)

Also accepts a measured circumference in millimeters.

Result

→

Nearest circumference

51.9 mm

Diameter

16.5 mm

Full EU to UK Ring Size Chart

Highlighted row = your match

EU (mm)	UK	Diameter (mm)

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Summary

Enter an EU ring size (mm circumference) to instantly find the equivalent UK letter size, with diameter and a full reference chart.

How it works

Enter the EU ring size, or a circumference you measured, in millimeters.
The tool matches it to the closest size on a standard EU-to-UK sizing chart.
The UK letter size, circumference, and diameter appear instantly.
If your value falls between two chart sizes, the tool shows how far off the nearest match is.
Scroll the reference table to see every size with your match highlighted.

Use cases

Buying a ring from a UK jeweler when you only know the EU size printed inside a ring.
Resizing a ring bought in Europe at a UK jewelry shop.
Converting a ring size from an EU online store before checkout.
Checking a ring inherited or gifted from abroad against a UK sizing chart.
Comparing a measured finger circumference to standard UK letter sizes.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu