On $75,000 of income filing single, taxable income is $60,400 after the $14,600 standard deduction, and 2024 federal tax is $8,341 — an 11.1% effective rate despite a 22% marginal bracket. US federal income tax is computed in slices: income above the standard deduction is taxed bracket by bracket, so only the dollars inside each bracket pay that bracket's rate.
Suppose you put the default values into Income Tax Calculator:
Plug those into the formula tax = Σ bracket-slice × rate, on income − standard deduction and the result is:
| Rate | Single (taxable income) | Married filing jointly (taxable income) |
|---|---|---|
| 10% | $0 – $11,600 | $0 – $23,200 |
| 12% | $11,600 – $47,150 | $23,200 – $94,300 |
| 22% | $47,150 – $100,525 | $94,300 – $201,050 |
| 24% | $100,525 – $191,950 | $201,050 – $383,900 |
| 32% | $191,950 – $243,725 | $383,900 – $487,450 |
| 35% | $243,725 – $609,350 | $487,450 – $731,200 |
| 37% | Over $609,350 | Over $731,200 |
IRS rate schedule, tax year 2024 · Source: IRS federal income tax rates and brackets
The calculator subtracts the 2024 standard deduction ($14,600 single, $29,200 married filing jointly), then walks taxable income through the seven 2024 brackets published in the IRS federal income tax rate schedule, taxing each slice at its own rate from 10% up to 37%. This progressive structure is why the effective rate (total tax ÷ total income) always sits below the marginal rate (the rate on the last dollar). Deliberately excluded: itemized deductions, credits such as the child tax credit or EITC, FICA payroll taxes, and all state and local income tax — each of which can move the real bill substantially.
References: IRS federal income tax rates and brackets.
Last reviewed July 2, 2026 · Editorial policy