You can see the 2017 tax brackets on the page below. For instance, if you are Single, taxable income between $9,326 to $37,950 is taxed at 15%.

You can look at your 2016 taxable income on line 43 of your 2016 1040 to see how close to the next bracket you are.

Also, your income is taxed in brackets. The amount in the 15% bracket is taxed at 15%. All of your income doesn't suddenly get taxed at a higher rate just because some of your income went into a higher bracket. (Just in case that is not clear)

http://www.bankrate.com/finance/taxes/tax-brackets.aspx

Keep in mind that your taxable income is dependent on your deductions. In some cases, increased income can reduce deductions.. which in turn increases taxable income even more than expected.

If you have more questions, tell us more about you.