US ring size 6

US size 6 has an inside diameter of approximately 16.5 mm and an inside circumference of 51.9 mm.

How to check whether size 6 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 16.5 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.