Just to add a bit to what PaulEA says in #44802, the number on Line 39 of your Form 1040 is your Taxable income, not your Adjusted Gross income or income that includes tax-free municipal bond interest and stuff like that.

So suppose, as PaulEA does in his example, that your gross is $50K and you are single and taking the standard deduction. Then that $50K is reduced by $4400 for the standard deduction and $2800 for a single person's exemption, making the taxable income $42,800. So it's even, a little bit, sort of, better than you might believe if you read Paul's post in total ignorance. But what he says is quite right.

Tax brackets are found on Page 71 of this year's Form 1040 Instructions.