Filing status changes more than you might expect
Single, married filing jointly, married filing separately and head of household each have their own standard deduction and bracket widths. Head of household — for unmarried people who pay more than half the cost of a home for a qualifying person — sits between single and joint. Married filing jointly here assumes your spouse has no wages; if you both work, run each salary separately or expect a combined bill closer to two single filers with wider brackets.
Biweekly is not the same as semi-monthly
Biweekly pay means 26 paychecks a year, every other Friday; semi-monthly means 24, usually on the 15th and the last day of the month. A biweekly check is smaller, but two months a year contain three of them. Pick your actual schedule in the result to see the right amount per check.
Why your paystub may not match
Employers withhold federal tax using IRS Publication 15-T and the choices on your W-4: extra withholding, other income, deductions you expect to claim, and the “multiple jobs” checkbox. This calculator skips those choices and shows the tax that is actually due for the year, which is what decides your refund. If the two differ a lot, update your W-4 rather than waiting for April.
Local income taxes
New York City and Yonkers residents pay a local income tax on top of state tax, and every Maryland county and many Indiana counties add a county rate. Choose your state and a “Local income tax” selector appears where our rules file lists localities. City wage taxes in Ohio, Pennsylvania and Michigan are not modelled yet; the state pages explain how they work.