If a raise pushed you into the "22% bracket" and you're bracing for 22% of your whole paycheck to disappear, the actual math is much friendlier than that. Here's exactly how US federal income tax is calculated layer by layer, why your real (effective) rate is always lower than your bracket rate, and how FICA payroll tax fits in separately.
How federal income tax brackets actually work
Quick answerUS federal income tax is progressive: your taxable income (gross income minus the standard deduction) is divided into layers, and each 2025 bracket — 10%, 12%, 22%, 24%, 32%, 35%, 37% — taxes only the slice of income that falls inside it. Being "in the 22% bracket" means only your last dollars are taxed at 22%; every dollar below that slice was already taxed at the lower rates that applied to it.
This is the single most common misunderstanding about income tax. A raise that pushes your top dollar into a higher bracket does not retroactively tax your entire income at that higher rate — it only applies the new rate to the income above the bracket threshold. Your marginal rate (the rate on your last dollar) and your effective rate (total tax divided by total income) are two different numbers, and the effective rate is always the lower one.
Taxable income, in plain terms: your gross income minus the standard deduction (or itemized deductions, if you use those instead). For 2025 the standard deduction is $15,000 for Single filers, $30,000 for Married Filing Jointly, and $22,500 for Head of Household — it's subtracted first, and only what's left gets run through the bracket layers.
Worked example: $75,000 gross income, Single filer
Quick answerAs an example calculation for a Single filer earning $75,000 in 2025: taxable income after the $15,000 standard deduction is $60,000. Layer by layer, that comes to a total federal tax of $8,114.00 — a marginal rate of 22% but an effective rate of only about 10.8% of gross income.
Here's how the $60,000 of taxable income actually splits across brackets, instead of being taxed at one flat rate:
Example only: $60,000 taxable income, Single filer, 2025 brackets
| Bracket | Income in this layer | Tax from this layer |
|---|
| 10% | $0 – $11,925 | $1,192.50 |
| 12% | $11,925 – $48,475 | $4,386.00 |
| 22% | $48,475 – $60,000 | $2,535.50 |
Add those three layers together and the total federal tax is $8,114.00. Compare that to a common (incorrect) shortcut of $75,000 × 22% = $16,500 — more than double the real result, because that shortcut wrongly applies the top bracket rate to every dollar instead of just the top slice. Mixing up "my bracket" with "my tax rate on everything I earn" is the single most common income-tax misconception, and it's exactly what a genuine marginal calculation avoids.
⚠ Worth noting: the 2025 bracket thresholds and standard deduction are adjusted for inflation every year by the IRS. The specific dollar figures in this article are 2025 numbers for illustration — always check the current tax year's thresholds before relying on any calculation for filing purposes.
FICA: the separate payroll tax most people forget about
Quick answerFICA (Social Security + Medicare) is a flat-rate payroll tax entirely separate from federal income tax, with no brackets or standard deduction. The employee share is 6.2% Social Security up to the 2025 wage base of $176,100, plus 1.45% Medicare with no cap, plus a 0.9% Additional Medicare Tax on wages above $200,000 (Single/Head of Household) or $250,000 (Married Filing Jointly).
Because Social Security tax stops entirely once wages exceed the annual wage base, high earners actually pay a lower effective FICA rate on their total wages than moderate earners do — the opposite of how progressive income tax brackets behave. On a $75,000 salary (below the 2025 wage base), FICA works out to the full 7.65% combined rate: 6.2% + 1.45%, with no Additional Medicare Tax since income is well under the $200,000 threshold.
How pre-tax contributions change your actual tax bill
Quick answer401(k), Traditional IRA, and HSA contributions are pre-tax: they're subtracted from income before brackets are applied, lowering taxable income and therefore federal tax. 401(k) and HSA contributions also reduce wages subject to FICA (since they're deducted through payroll); a Traditional IRA only lowers federal taxable income, since IRA contributions aren't made through payroll.
This distinction matters if you're comparing take-home pay estimates: putting $5,000 into a 401(k) shrinks both your federal taxable income and your FICA wages, while putting the same $5,000 into a Traditional IRA only shrinks your federal taxable income, leaving your FICA bill unchanged. Neither is "better" universally — it depends on your employer's plan, contribution limits, and your broader retirement strategy — but knowing which wages each deduction actually reduces helps you interpret a take-home pay estimate correctly.
Frequently asked questions
How is federal income tax calculated?
US federal income tax uses a marginal (progressive) bracket system. Your taxable income (gross income minus the standard or itemized deduction) is divided into layers, and each layer is taxed only at its own bracket's rate — not your whole income at one flat rate. The bracket rates for 2025 are 10%, 12%, 22%, 24%, 32%, 35%, and 37%, with thresholds that depend on your filing status.
What is the difference between marginal and effective tax rate?
Your marginal tax rate is the rate applied to your last (highest) dollar of taxable income — the bracket you 'are in'. Your effective tax rate is your total tax divided by your total income, which is always lower than your marginal rate because lower brackets are taxed at lower rates first. Being 'in the 22% bracket' does not mean you pay 22% of your entire income.
How much federal tax do I pay on $75,000 as a Single filer?
As an example calculation, a Single filer with $75,000 of gross income in 2025 has taxable income of $60,000 after the $15,000 standard deduction. Applying the brackets: 10% on the first $11,925 ($1,192.50), 12% on the next $36,550 ($4,386.00), and 22% on the remaining $11,525 ($2,535.50) — a total federal income tax of $8,114.00. The marginal rate is 22%, but the effective rate on gross income is only about 10.8%.
What is FICA and how is it different from income tax?
FICA (Federal Insurance Contributions Act) tax funds Social Security and Medicare and is separate from federal income tax, with no brackets or standard deduction. The employee share is 6.2% for Social Security (up to the 2025 wage base of $176,100) plus 1.45% for Medicare with no wage cap — 7.65% combined on wages up to the Social Security wage base — plus an Additional Medicare Tax of 0.9% above $200,000 ($250,000 if Married Filing Jointly).
How do 401(k) and HSA contributions lower my tax bill?
401(k), Traditional IRA, and HSA contributions are pre-tax: they are subtracted from your income before federal tax brackets are applied, lowering your taxable income and therefore your federal income tax. 401(k) and HSA contributions are also excluded from wages subject to FICA because they are deducted through payroll, while Traditional IRA contributions only reduce federal taxable income since they are not made through payroll.