The county assessors office has a group of staff appraisers that use a mass appraisal system to determine the market value of a property. It is not as involved as if you hired an independent appraiser to value your property. In GA, your assessed value will be 40% of the market value. To figure your tax rate, you would simply take 40% of your market value and multiply it by the current millage rate for the county. Go to your county tax assessor website for more details.