This website should help - for Fulton county https://www.fultoncountytaxes.org/fultoniwr/05_depts_our_off
the primary counties in "metro" Atlanta are Fulton, Cobb, Dekalb
The calculation varies (of course) if you are in an incorporated or unincorporated area of each county.
For example, two "new" cities were just created in North Fulton - John's Creek and Milton -
Feel free ot get in touch directly if you have specific areas and I can get you that information.
Otherwise, you can just search for the county/city and tax assessment rate.