Income Tax Calculator
Calculate income tax owed by applying a flat tax rate to total income — a simplified shortcut for estimating tax burden in flat-rate jurisdictions or for back-of-envelope marginal-rate math. Use it for quick gut-checks; for real US federal tax which uses progressive brackets, use a dedicated tax-bracket calculator instead.
Last updated: May 2026
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About this calculator
The formula is: tax owed = income × rate ÷ 100. This is a flat-rate calculation, where the same percentage applies to every dollar of income. It accurately models flat-tax jurisdictions (Massachusetts and Illinois at the US state level, Bulgaria, Russia, several other countries at the national level), as well as flat-rate components of US federal taxation (Social Security at 6.2%, Medicare at 1.45%, additional Medicare at 0.9% above thresholds). But it does NOT correctly model US federal income tax, which is progressive — the first portion of income is taxed at 10%, the next portion at 12%, then 22%, 24%, 32%, 35%, and 37% for 2024 (single filer brackets). Under a progressive system, the "rate" you would plug into this calculator would be the EFFECTIVE rate (total tax owed divided by total income), which is lower than your top marginal rate because lower brackets apply to your first dollars. For example, a single filer earning $100,000 in 2024 has a 24% marginal rate but only about 14% effective rate. Edge cases: a rate of 0% returns zero tax; a rate of 100% confiscates all income (not a real-world rate but mathematically allowed); negative rates would model refunds, which is also mathematically allowed but conceptually odd. For accurate tax estimation in any progressive-bracket country (most developed economies), use a calculator that applies the full bracket schedule rather than this flat-rate shortcut.
How to use
Example 1 — Flat-tax state. You earn $85,000 of taxable income in Illinois, which has a flat state income tax rate of 4.95%. Enter 85000 for Income and 4.95 for Tax Rate. Result: $4,207.50. Verify: 85000 × 4.95 / 100 = $4,207.50. ✓ This is exactly correct for a flat-tax state. For US federal tax on the same $85,000 (taxable), you would owe approximately $13,640 under 2024 single-filer brackets — about 16.0% effective rate — using progressive math this calculator doesn't handle. Example 2 — Estimating effective federal rate. You researched your effective federal tax rate for last year and it was 17.8% on gross income of $115,000. Use the calculator to project this year's federal tax at the same effective rate (assuming similar income). Enter 115000 and 17.8. Result: $20,470. Verify: 115000 × 17.8 / 100 = $20,470. ✓ This is a reasonable approximation if your income, deductions, and tax laws stay similar; for a precise figure, use a full federal-tax calculator with actual brackets, filing status, and current-year deductions.
Frequently asked questions
Does this calculator handle US federal income tax brackets?
No. US federal income tax is progressive, meaning different portions of your income are taxed at different rates (10%, 12%, 22%, 24%, 32%, 35%, 37% in 2024). This calculator applies a single flat rate to all of your income, which is mathematically wrong for any progressive-bracket country. To use this calculator usefully for federal tax, plug in your effective tax rate (total tax owed ÷ total income) — that produces the right total even though it doesn't correctly model how the brackets actually work. For a real bracket-based calculation, use a dedicated tax-bracket tool that applies the schedule to each portion of income. The IRS tax tables in Publication 17 (irs.gov) are the authoritative source for accurate calculations.
What is the difference between marginal and effective tax rate?
The marginal tax rate is the rate applied to your next dollar of income — for a 2024 single filer with $75,000 of taxable income, the marginal rate is 22% because the next dollar falls into the 22% bracket (which runs from $47,150 to $100,525). The effective tax rate is the average rate across all your income — total tax divided by total income, typically much lower than the marginal rate because lower brackets apply to your first dollars. For that same $75,000 filer, the effective federal rate on taxable income is roughly 15.7% (and even lower as a fraction of gross income before deductions). Marginal rate is the relevant figure for decisions about additional income (taking a side job, selling an asset); effective rate is the relevant figure for total tax burden and budgeting.
What is taxable income vs. gross income?
Gross income is all the money you received during the year from all sources before any deductions. Taxable income is what remains after subtracting above-the-line deductions (traditional 401(k) contributions, traditional IRA contributions, HSA contributions, student-loan interest up to $2,500), the standard deduction or itemized deductions (whichever is larger), and the qualified business income deduction (if self-employed). Federal income tax is calculated on taxable income, not gross income. For a typical W-2 employee with no special deductions taking the 2024 single-filer standard deduction of $14,600, taxable income is gross income minus 401(k) contributions minus $14,600. To enter "income" into a tax calculator, always confirm whether the calculator expects gross or taxable; this calculator works the same either way but the result is only meaningful with the correct base.
What are the most common mistakes people make estimating income tax?
The biggest is using a single flat rate to estimate federal tax — the US system is progressive, so flat-rate math overstates tax for low and middle earners (whose first dollars are taxed at 10–12%) and understates for high earners (whose top dollars are taxed at 32–37%). The second is confusing gross and taxable income; federal tax is applied to taxable income, and ignoring the standard deduction (or itemized deductions, 401(k) contributions, etc.) overstates tax owed. The third is forgetting state and local taxes; states range from no income tax (Texas, Florida, Washington) to flat rates (Massachusetts, Illinois, Colorado) to progressive (California, New York, federal-style). The fourth is forgetting FICA (Social Security 6.2% + Medicare 1.45%, employer matches but for self-employed both halves apply) — these are 7.65% of wages on top of income tax. The fifth is forgetting tax credits that reduce tax owed dollar-for-dollar (Child Tax Credit, EITC, education credits) — they're not deductions and they aren't modeled in this calculator at all.
When should I not use this calculator?
Skip it for any real US federal income tax estimation — use a bracket-based calculator that applies the full progressive schedule, or the IRS Tax Withholding Estimator at irs.gov/withholding. It is the wrong tool for self-employed estimated tax payments, which include SE tax (15.3% on net earnings) in addition to income tax. Do not use it for state taxes without checking your state's system — if you're in a progressive-bracket state, the flat-rate shortcut is just as wrong as for federal. It also doesn't handle tax credits, AMT, capital gains rates, or any of the specialized rules that affect real tax bills. For tax planning decisions involving real money (Roth conversions, asset sales, retirement-account withdrawals, equity-comp events), use full tax-prep software (TurboTax, FreeTaxUSA, H&R Block) or consult a CPA. This calculator is a back-of-envelope tool for flat-rate jurisdictions or effective-rate approximations only.