You will owe 15.3% of your earned income plus income tax at your marginal rate. As a rule of thumb withholding about 30% usually works out.
Much depends on your status and amount you make for the year.
Tax rate for Single taxpayer is below: under $90K 15% to 20%. copy the below link to your browser.
If you can estimate your income, subtract the standard deduction for the filing status you use.
So if you think you'll make 50,000 and your filing Married Filing Jointly, your Standard Deduction will be 14,600.
That will leave 35,400 taxable income.
Lets say you're in the 12% tax bracket that would be 4,248 Income tax you would owe.
On top of that, since you are self-employed, you pay your own FICA tax (Social Security) which is 15.3% although you also get a deduction for half that amount.
As stated above, 30% should cover your tax payments, but there are other factors such as tax credits (like the Child Tax Credit) and other income sources, like wages and Capital Gains.
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