Well, curvy girls are usually anyone 170 lbs plus.. Now my ex gf's were both curvy they were both over 200 lbs. Some could call a certain few of who I dated to be considered overweight, but it made no difference to me.

This is a bit of a general chart, but it gives you a good idea of whereabouts you should be, based on your height.

This chart doesn't take into account things like muscle mass for example.