205/60R15 Tires
205mm wide radial tires with a 60% aspect ratio on 15 inch rims.
The diameter of the rims is measured inside the lip, on the surface where the bead of the tire sits. You can't measure this without taking the tire off. Read the size off the sidewall of your tires. That will tell you the diameter of the rims (as shown above).
Also, many rims will have their diameter, profile, and width stamped in them. This is usually in an inconspicuous spot, such as near the lug nuts or even on the back side. It might look something like: 6½J×15. That is 6½ inches wide by 15 inches in diameter with a "J" profile lip.
Just go to tirerack.com and select your car. They sell rims, tires, etc. and can tell you what will fit and what you can substitute while maintaining ground clearance and speedometer/odometer accuracy. There are other factors to consider, such as fender and suspension clearance, but whatever they say should fit your car, should. They even have an option to preview the rims on your car.