A bonus may push your total income into a higher tax bracket, but bonuses aren't by themselves taxed at a higher rate.
If you are going to recalculate 2017 by yourself, you will either have to download forms and instructions for 2017 from <a rel="nofollow" target="_blank" href="
http://www.irs.gov">www.irs.gov</a>, or buy the CD/Download version of TurboTax 2017. Depending on the complexity of your tax return, it could just be as simple as subtracting from your 2017 AGI and looking up the tax due in the tax tables, or much more complicated - impossible for me to say.
