Converters

Ring size converter

Find your ring size from your finger circumference, and its US, UK and diameter equivalents.

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Copy this code and paste it into your page (WordPress, Wix, Webflow, HTML…). It's free: please keep the link to HOD Calc.

How it works

French size = circumference in mm. Diameter = circumference / π. US size ≈ (circumference − 36.5) / 2.55. Measure at the end of the day, when fingers are slightly bigger.

Results are for guidance only and do not replace professional advice.

Worked example

With the default values:

  • Finger circumference (mm)54

you get:

  • French / Belgian size54
  • Inner diameter17.2 mm
  • US / Canada size7
  • UK sizeN

Frequently asked questions

How does the “Ring size converter” tool work?

French size = circumference in mm. Diameter = circumference / π. US size ≈ (circumference − 36.5) / 2.55. Measure at the end of the day, when fingers are slightly bigger.

What do I need to enter?

Just fill in: finger circumference. The result updates as you type.

Can you give an example?

Finger circumference (mm): 54 → French / Belgian size: 54; Inner diameter: 17.2 mm.

Is this calculator free, and is my data private?

Yes. HOD Calc is completely free with no sign-up. The calculation runs in your browser: nothing you type is sent or stored.