US ring size 10

US size 10 has an inside diameter of approximately 19.8 mm and an inside circumference of 62.1 mm.

How to check whether size 10 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 19.8 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.