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Ring Size Converter

Convert ring sizes between US, UK and EU systems, with diameter and circumference in millimeters.

Ring size

Pick the system you know, then enter the size.

Converted sizes
-

Enter a size to convert.

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How the systems relate

EU sizes are simply the inside circumference in millimeters, so an EU 54 ring measures 54 mm around. US sizes step about 0.8128 mm of diameter per size, and UK letters step about 1.27 mm of circumference per letter. The converter works through millimeters to move between all three.

Why you should measure, not guess

Half a US size is only 0.4 mm of diameter, yet it is the difference between comfortable and unwearable. Finger size changes with temperature and time of day, so measure in the afternoon when fingers are warmest.

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Ring Size Converter FAQs

What is my ring size if I do not know it?
Wrap a strip of paper around the finger, mark where it overlaps, and measure the length in millimeters. That length is your EU size and converts to US and UK above.
Are US and UK ring sizes the same?
No. US sizes are numbers (3 to 13) and UK sizes are letters. A US 7 is roughly a UK N and an EU 54.
Should I size up for wide bands?
Yes, wide bands fit tighter. Go up half to one full US size for bands wider than about 6 mm, especially for comfort fit styles.
Do ring sizes differ for men and women?
The scales are unisex. Average women's sizes run US 5 to 7 and men's US 9 to 11, but the conversion math is identical.
Why does my ring fit differently in summer?
Fingers swell in heat and shrink in cold. A ring that fits perfectly in winter may feel tight in summer, so measure at a neutral temperature.
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