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Ring Size Converter

US, UK, EU, Japan and India ring sizes, from a measurement or a size you know.

Ring size
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Quick Tool Overview

The Ring Size Converter turns a size in any national system — or a measurement in millimetres — into all the others, with a full chart and advice on measuring a finger properly.

What it does
Converts ring sizes between countries
You give it
A US, UK, EU or Japanese size, or millimetres
You get back
Every other size, diameter and circumference
Best for
Ordering a ring from another country
Converters Free, unlimited use No sign-up Runs in your browser

About the Ring Size Converter

Ring sizes are one of the few things with no international standard at all. The United States counts in numbers and half sizes, Britain and Australia use letters, Europe uses the circumference in millimetres, and Japan, India and China use a third numbering altogether. Order from the wrong one and the ring does not fit.

Enter a size in any system — or the measurement itself, as the inside diameter or the distance around the inside — and get all of them, along with a chart from US 4 to US 13. Every system is derived from that one measurement, so once you have it in millimetres the rest follows. There are notes on how to measure a finger at home, when to size up for a wide band, and why the time of day matters.

Key features of the Ring Size Converter

Five systems

US and Canada, UK and Australia, Europe, Japan, India and China.

Half sizes

UK letters include the half sizes, so US 7 reads as N½ rather than N.

From a measurement

Enter the inside diameter or circumference straight from a ruler.

Full chart

US 4 to 13 side by side with every other system.

Fitting advice

When to size up, and why the time of day changes the answer.

How to use the Ring Size Converter

  1. 1

    Enter a size or a measurement

    A US number, a UK letter, or millimetres.

  2. 2

    Say which system it is

    So the conversion starts from the right place.

  3. 3

    Read every other size

    US, UK, EU, Japan and India, plus diameter and circumference.

  4. 4

    Check the chart

    The full table from US 4 to 13 is underneath.

Frequently asked questions

Wrap a strip of paper around the finger, mark where it overlaps, and measure that length in millimetres. That is the inside circumference — enter it and every size follows.

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