US → mm · Ring Size

Ring Size Converter

Convert ring sizes between US, UK, EU and JP to diameter in millimeters and centimeters for jewelry sizing.

Amount

Result

Common conversion	Result

About Ring Size conversion

Ring sizes differ by country: a US size 7 has a diameter of about 17.3mm, EU size 54 corresponds to 54mm circumference (about 17.2mm diameter), and UK/JP sizes follow similar scales with slight offsets.

Enter a size in one system and instantly see the others plus the diameter in millimeters and centimeters, perfect for online jewelry shopping or resizing.

Units supported: Diameter mm, Diameter cm, US Ring size, UK Ring size, EU Ring size (circumf mm), JP Ring size.

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Frequently asked questions

What units can I convert with the Ring Size converter?

Diameter mm, Diameter cm, US Ring size, UK Ring size, EU Ring size (circumf mm), JP Ring size.

How accurate is this ring size converter?

This converter uses standard international definitions for every ring size unit, so results are precise to several decimal places, accurate enough for cooking, travel, homework, or any everyday use.

Can I convert in both directions?

Yes, enter a value in either field and the other updates instantly. You can also tap the swap button to flip the two units, or use the copy-link button to share this exact conversion.