A ring can be sized up by a maximum of two sizes. Most rings, however, can only be brought up by one size.
The degree to which a ring can be resized depends largely on the nature of the band. If it is a plain band, it is much easier for the jeweler to increase the ring size. Bands encrusted with jewels or embellishments are more elaborate, and therefore more difficult to alter.
To make a ring larger by more than one size, a jeweler usually needs to add a piece of metal that matches the original band. This will make the ring fit looser on the finger.