Millage is also known as the tax rate and is set by the county government. The millage rate is derived by dividing the county's operating budget by the total assessed value in the county. A millage rate of 35 mills, or $35.00 per thousand, means that the assessed value of the property is multiplied by $35.00 for each thousand dollars of the assessment.

The tax rate is expressed in mills for property. One mill produces $1.00 tax for every $1,000 worth of property value. The rates for each county is set annually by the Board of County Commissioners, or other governing authority of the taxing jurisdiction, and by the Board of Education. Rockdale County calculated the millage rate by totaling the rates of the following taxing jurisdictions: State (.25 mills), county school (21.48 mills), city (9.9 mills) and county (14.69 mills). The total county's millage rate is 46.32, and unincorporated city millage rate is 36.42.

Example:
The assessed value (40 percent of the fair market value) of a house that is worth $100,000 is $40,000. In a county where the millage rate is 25 mills the property tax on that house would be $1,000; $25 for every $1,000 of assessed value or $25 multiplied by 40 is $1,000.