Quick rule of thumb that I have always used: Review your last year's return. See how much you paid last year- netted against a refund you may have received. Then take this figure and divide by what you earned that year. You will come up with a percent. Multiply this percent by what you expect to earn this year. This should get you really close assuming your income has not changed dramatically. Bear in mind that for most people tax rates will decline a little from last year. But this method should get you pretty close.