US ring size 11

US size 11 has an inside diameter of approximately 20.6 mm and an inside circumference of 64.6 mm.

How to check whether size 11 fits

Measure the inside diameter of a ring that already fits the intended finger. Measure straight across the widest inside point—do not include the metal. Compare that measurement with 20.6 mm.

This is a jewellery-size conversion, not a guarantee of fit. Finger size changes with temperature and time of day; wide bands often need extra room.