UK ring size to EU ring size
Turn a UK letter into the EU number a European or Gulf jeweller uses.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter uk size.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Circumference = 37.5 + 1.25 × letter index (A = 0), plus 0.625 for a half size. The EU size is the circumference rounded to a whole number.
Example
Inputs: UK size = N. Result: EU size (ISO): 54; Inner circumference: 53.75 mm; Inner diameter: 17.11 mm.
Limits and caveats
- Sizes are rounded to the nearest step of each system, and shop mandrels can differ slightly.
Questions about this tool
What is UK N in EU sizes?
Its circumference is 53.75 mm, so about EU 54.
How big is UK size C?
Size C is exactly 40 mm in circumference under the British scale.
Is the rounded EU size enough?
Usually, but a UK half size can fall between two EU numbers, so check the exact circumference.