Use this calculator to figure the self-employment tax owed on a given amount of income.
For 2011, the first $106,800 of net income from self-employment is subject to a 13.3% tax, which includes the Social Security and Medicare health insurance taxes. For 2012, the first $110,100 is subject to a 13.3% tax rate. Net self-employment income above these amounts is only subject to the 2.9% Medicare tax. And, of course, you will also owe income tax. Note that the 13.3% rate for 2011 and 2012 is lower than the normal 15.3% rate, thanks to a temporary rate reduction.