Help on measuring Tire Specs

[sk8r3124]

I am looking on getting some help. Come summer I need to pick up some new low profiles for the summer car and I don't know the specs I needs. I am new at this, and I know it is more than just needing 18" rubber. I need to figure it out in the actual format (eg. 205/55R18) I figure the R18 means 18" but what does the other stuff mean?

I just want to figure out the specs of my current tires, so I can buy new ones with the same specs

[GQBalla]

http://mistupid.com/automotive/tiresize.htm

[sk8r3124]

Thanks

[scat19]

Width/height in % of width/diameter!