Craft & Design
Ring Size Converter
Convert between US, UK, EU, and measured diameter or circumference — with fit advice.
Ring Size Converter
Inputs
Results
US size
7
UK / AU size
N½
EU (ISO)
54
Inner diameter
17.30 mm
Inner circumference
54.3 mm
How to use this
Wrap a strip of paper around the base of your finger and mark where it overlaps — the length in mm is your circumference. Measure at the end of the day when fingers are slightly larger, and size up for knuckle clearance.
Formula
circumference = inner_diameter × π
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Formula
circumference = diameter × π