The general rule would be about 20% for federal taxes.
If you live in a state with a personal income tax then check the tax rates for your state for how much to set aside for the state income taxes.
You can also use the worksheets for the federal estimated taxes in Form 1040-ES - <a rel="nofollow" target="_blank" href="https://www.irs.gov/pub/irs-pdf/f1040es.pdf">https://www.irs.gov/pub/irs-pdf/f1040es.pdf</a>
Payment of estimated federal taxes can be made either using Form 1040-ES or the IRS website for payments - <a rel="nofollow" target="_blank" href="https://www.irs.gov/payments">https://www.irs.gov/payments</a>