You are in 2 or 3 capital gains tax brackets depending on your filing status and standard or itemized deductions--0%, 15%, and 20%. When the sum of your taxable ordinary income plus capital gains reaches the top of the 0% rate for your filing status, then the amount of capital gains above that limit and up to the top of the 15% limit are taxed a 15%. Any amount above the top of the 15% bracket is taxed at 20%. The additional 3.8% is added on top for amounts above the non taxable limit for your filing status.
