How federal income tax actually works
The US tax system is progressive and marginal: your income is divided into bands, and each band is taxed at its own rate. Reaching the 22% bracket does not mean all your income is taxed at 22% — only the dollars inside that band are. The blend of all those rates is your effective rate, which is what you actually pay.
The order of operations
Gross income − pre-tax contributions − deduction = taxable income. Taxable income is run through the brackets to get federal tax. FICA is added on top, computed on gross wages. The total, divided by gross income, is your effective rate.
What makes this calculator different
- A true bracket-by-bracket breakdown. Most calculators give you a single number. We show how many dollars land in each bracket and the tax from each — so the marginal-vs-effective distinction is obvious, not abstract.
- FICA broken out. Social Security and Medicare are real money out of your check, so we surface them separately instead of hiding them.
- Pre-tax impact, made visible. See exactly how 401(k)/HSA contributions lower your taxable income — and why they don’t cut FICA.
- Marginal and effective, side by side. Two stat cards put the headline myth to rest: a raise into a new bracket never lowers your take-home pay.
Frequently asked questions
What’s the difference between my marginal and effective tax rate?+
Your marginal rate is the rate on your last dollar of income — the top bracket you reach. Your effective rate is the total tax you owe divided by your total income, which is always lower. For example, a single filer earning $85,000 hits the 22% bracket, but only the income above ~$48,475 is taxed at 22%; the rest is taxed at 10% and 12%. That’s why their effective federal rate lands closer to 12–13%, not 22%. This calculator shows both, plus the exact dollars taxed in each bracket.
Should I take the standard deduction or itemize?+
Take whichever is larger. For 2025 the standard deduction is $15,000 (single), $30,000 (married filing jointly), and $22,500 (head of household). You should itemize only if your deductible expenses — mortgage interest, state and local taxes (capped at $10,000), charitable gifts, and certain medical costs — add up to more than the standard amount. Most filers come out ahead with the standard deduction, but enter an itemized total to compare.
What is FICA and why is it separate from income tax?+
FICA is the payroll tax that funds Social Security and Medicare. For 2025 it’s 6.2% for Social Security on wages up to $176,100, plus 1.45% for Medicare on all wages, with an extra 0.9% Medicare surtax on wages above $200,000 (single/head) or $250,000 (married). It’s calculated on your gross wages — separately from income tax and with its own rules — so we break it out so you can see your full tax burden, not just income tax.
How do pre-tax 401(k) and HSA contributions lower my taxes?+
Traditional 401(k), HSA, and similar pre-tax contributions come out of your pay before federal income tax is calculated, so they directly reduce your taxable income — and the savings are biggest at your marginal rate. Note one wrinkle: 401(k) contributions still count as FICA wages, so they cut your income tax but not your Social Security and Medicare tax. Enter an amount to see exactly how much your taxable income (and bill) drops.
Will a raise that pushes me into a higher bracket leave me with less money?+
No — this is the most common tax myth. The US uses a progressive, marginal system: only the income above each bracket threshold is taxed at the higher rate. A raise never causes your existing income to be taxed more, and your take-home pay always goes up. The bracket-by-bracket breakdown above makes this concrete by showing that only the new top slice of income is taxed at the higher rate.
Disclaimer: This is a 2025 federal income tax estimate for educational purposes only. It uses a simplified flat state rate, ignores tax credits, the AMT, the net investment income tax, capital-gains treatment, and other taxes, and assumes ordinary wage income. Your actual liability depends on your full return. This is not tax advice — consult a qualified tax professional.