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mm to ring size

Measured your finger in mm? A 54 mm inner circumference is a US 7.

Circumference (mm) to ring size

CircumferenceInner ØUSUK
49.3 mm15.7 mm5
51.9 mm16.5 mm6
54.4 mm17.3 mm7
57.0 mm18.1 mm8Q
59.5 mm18.9 mm9
62.1 mm19.8 mm10
The EU/ISO ring size is the inner circumference in mm, so 54 mm circumference is an EU 54. Measured diameter instead? Multiply by π (3.14) for circumference.

Frequently asked questions

What ring size is 54 mm?

A US 7 (UK N½, EU 54).

How do I convert mm to ring size?

If you measured circumference, the mm value is the EU size. If diameter, multiply by 3.14 first.