Step-by-Step Breakdown of the Components
The first useful distinction is between federal income-tax withholding and payroll taxes.
Federal income-tax withholding is an advance payment toward your federal income-tax liability. Employers calculate it using payroll withholding methods and the information supplied on Form W-4. The IRS's 2026 Publication 15-T provides the current withholding tables and methods.
Taxes, Deductions, and Adjustments
FICA is separate. For 2026, employees generally pay 6.2% Social Security tax on covered wages up to $184,500 and 1.45% Medicare tax on covered wages. Medicare has no wage-base limit. An employer must also begin withholding the 0.9% Additional Medicare Tax from wages paid to an employee above $200,000 during the year. turn0search5■ Then there may be state and local income taxes. Some states impose individual income taxes; others do not. Local income taxes can also apply in particular jurisdictions.
Suppose your gross paycheck is $4,000. Your federal withholding might be one amount, FICA another, and state or local tax another. If you also contribute to a retirement plan or pay for health insurance, your take-home amount can fall further. The resulting percentage of gross pay that disappears from your check is therefore a combination of several different systems.
This is why a headline such as “the average worker pays X% of every paycheck in tax” can be misleading. Your paycheck is not simply gross pay multiplied by one tax rate.
Estimating and Verifying Your Paycheck
There is another important distinction: withholding is not necessarily the same as your final tax liability. Your tax return ultimately determines the federal income tax you owe after considering the rules that apply to your situation. A refund can mean you paid more through withholding than your final liability; a balance due can mean you paid less.
For paycheck planning, the better question is not “What percentage should I expect?” It is “What will my gross pay be, what withholding applies, what deductions do I have, and what will actually reach my account?”
That is the question a good paycheck calculator should help you answer.