Use this calculator to estimate your self-employment taxes for 2013. Normally these taxes are withheld by your employer. However, if you are self-employed, operate a farm or are a church employee you may owe self-employment taxes. This calculator uses 2013 tax tables and should not be used for estimating 2012 self-employment taxes. Please note that the 2013 self-employment tax is 12.4% for the FICA portion and 2.9% for Medicare.