Ring Size Converter

What you know

Value

Result

Russian size17
American size6.61
European size53.4
Diameter, mm17
Circumference, mm53.41
What mattersThe Russian size is the inner diameter in millimetres and the European one is the circumference. Measure in the evening: fingers swell slightly through the day.

The Russian size is simply the diameter

Converts a ring size between the Russian, American and European systems from the inner diameter or the circumference.

The Russian system is the most transparent of the three: a ring size is the inner diameter in millimetres. Size 17 means a 17-millimetre opening, and no table is needed to work that out.

The European system uses the circumference and the American one its own linear scale, where a size step is roughly 2.55 millimetres of circumference. They convert through the diameter, which is the only physical quantity involved.

What this calculator shows

Russian, American and European sizes
Inner diameter and circumference in millimetres
Conversion from any direction: diameter, circumference or American size

What to keep in mind

The American scale is treated as linear in circumference, so it produces fractional values between the standard half sizes.
Measure in the evening at room temperature: fingers swell slightly through the day and shrink in the cold.

FAQs

How do I find a ring size at home?

Wrap a strip of paper round the finger, mark the join and measure the length. Divide by 3.14 for the diameter, which is the Russian size.

What ring size is most common?

16 to 18 for women and 19 to 21 for men. The spread is wide, and any ring still has to be fitted to the actual finger.

How does the European size work?

It is the circumference in millimetres, which is the Russian size multiplied by 3.14. A Russian 17 is about a European 53.

When should I measure?

In the evening and in the warm: fingers swell slightly through the day and thin in the cold. A ring sized on a cold morning may not come off by evening.

Worked example

A size seventeen ring

Input: 17 mm inner diameter

Output: Russian 17, American 6.6, circumference 53.4 mm

Note: The American size lands between six and seven, so a shop will make you pick one. Half a size is a little over a millimetre of circumference — noticeable on the finger.

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Ring Size Converter

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