What is ring size 9 in mm?

US ring size 9 is 19.0 mm inner diameter and 59.5 mm circumference (EU 59.5, UK R½, Japan 18).

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Ring size 9 in mm

Inner Ø19.0mm

Circumference59.5mm = EU/ISO

UKR½

JP · CN18

IT · ES · CH19.5

US ring size 9 has an inner diameter of 19.0 mm and an inner circumference of 59.5 mm. The EU/ISO size is that circumference (59.5); in the UK it’s R½, in Japan/China 18, and in Italy/Spain/Switzerland 19.5 (circumference minus 40). Not sure of your size? Measure a ring you own with the on-screen ring sizer.