The Gross Domestic Product (GDP) for a country is a total market value of all domestically produced goods and services. The GDP growth rate indicates the current growth trend of the economy. When calculating GDP growth rates, the U.S. Bureau of Economic Analysis uses real GDP, which equalizes the actual figures to filter out the effects of inflation. Using real GDP allows you to compare previous years without inflation affecting the results.
Look up the real GDP for two consecutive years. These figures are found on the U.S. Department of Commerce Bureau of Economic Analysis' website.
Subtract the first year's real GDP from the second year's GDP. As an example, the real GDP in the U.S. for 2009 and 2010 were $12.7 trillion and $13.1 trillion, respectively. Subtracting the 2009 figure from the 2010 figure results in a difference of $384.9 billion.
Divide this difference by the first year's read GDP. In the example, you would divide $354.9 billion by $12.7 trillion, which gives you an annual growth rate of 0.030, or 3 percent.