Ring size converter
Convert ring sizes between US numbers, UK letters, EU circumference and Japanese sizes, or work from a measured diameter.
That's 1.05× as big as an average women’s ring, while an average men’s ring is 1.1× bigger. That is about 17.32 mm across the inside.
What it means
How big is that ring?
Measure a ring that fits across its inside, or wrap a strip of paper around the finger. Fingers swell in heat, so measure warm.
Every unit
Your ring size in every system
Learn
Three things worth knowing
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EU size is just the circumference
A size 52 ring measures 52 mm around the inside, which is 16.6 mm across. US 6 is close to that.
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Letters and numbers
Britain and Ireland size rings by letter, America by number, and Europe by the circumference itself. Jewellers’ mandrels carry all three, and neither side has moved.
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Measure the finger, not the ring
A wide band needs about half a size larger than a thin one. And fingers change size by a full size between a cold morning and a hot afternoon.
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Popular ring size conversions
Background
About ring sizes
The EU/ISO size is simply the inner circumference in millimeters, which makes it the honest one. US sizes step by 2.55 mm of circumference, and UK sizes use letters, half a US size apart.