How Federal Income Tax Is Calculated
The US uses a progressive, bracketed system: your income is taxed in slices, and each slice is taxed at its own rate. You do not pay your top rate on every dollar — only on the dollars that fall inside the top bracket you reach. This calculator applies the official 2025 federal tax brackets and the standard deduction for your filing status, then reports both your marginal rate (the rate on your last dollar) and your effective rate (total tax divided by total income), which is always lower.
Taxable Income and the Standard Deduction
Your tax is not calculated on your gross income. First, subtract any above-the-line deductions such as traditional 401(k), HSA, or deductible IRA contributions, then subtract the standard deduction. What remains is your taxable income. For 2025 the standard deduction is $15,000 for single filers, $30,000 for married filing jointly, and $22,500 for head of household.
Taxable Income = Gross Income − Pre-tax Deductions − Standard Deduction2025 Federal Tax Brackets (Single)
10% up to $11,925 · 12% to $48,475 · 22% to $103,350 · 24% to $197,300 · 32% to $250,525 · 35% to $626,350 · 37% above. Brackets roughly double for married filing jointly. These figures are inflation-adjusted each year by the IRS.
What This Estimate Does and Does Not Include
This is a federal income-tax estimate based on the standard deduction. It does not include state or local income tax, Social Security and Medicare (FICA) payroll taxes, the additional Medicare tax, itemized deductions, tax credits (such as the Child Tax Credit or EITC), or capital-gains treatment. Use it as a planning baseline, not as tax-filing advice — confirm specifics with a tax professional or the IRS.