How Income Tax Is Calculated: Brackets and Rates Explained
Published 1/8/2026 · 2 min read · Finance calculators
Income tax is progressive: your income is split across brackets, and each slice is taxed at that bracket's rate. Your marginal rate applies only to the top slice, while your effective rate — total tax divided by total income — is always lower. A raise is taxed at your marginal rate, never at 100%, so you always keep most of it.
Understand marginal vs. effective tax rates, how progressive brackets work, and why a raise never gets fully taxed away — with a clear worked example.
Progressive brackets, slice by slice
Most countries tax income progressively. Your income is cut into slices by the bracket thresholds, and each slice is taxed at its own rate. In the US, federal brackets rise from 10% up through 37%; the first dollars are taxed lightly and only income above each threshold is taxed at the higher rate. Nothing pushes your earlier income into a higher rate.
Marginal vs. effective rate
Your marginal rate is the rate on your last dollar earned — the top bracket you reach. Your effective rate is the total tax you pay divided by your total income. Because the lower slices are taxed at lower rates, the effective rate is always below the marginal rate. Someone in a 24% marginal bracket might pay an effective rate closer to 15%.
Allowances and deductions
Before brackets apply, part of your income is usually shielded. In the US this is the standard deduction; elsewhere it's a tax-free personal allowance or a family-based quotient. Deductions lower your taxable income before the rates hit, so they save tax at your marginal rate — a $1,000 deduction in a 24% bracket saves $240.
Worked with our own calculator
Income tax calculator
Given
- Annual taxable income
- $17,500.00
- Household parts
- 0.5
Result
- Income tax
- $1,893.12
- Effective rate
- 10.82%
These figures are produced by the calculator below, not typed in by hand — they are recomputed whenever the tool changes.
Run it on your own figures →Frequently asked questions
- Will a raise put me in a higher bracket and cost me money?
- No. Only the portion of income above the new threshold is taxed at the higher rate, so a raise always leaves you with more take-home pay.
- What's the difference between a deduction and a credit?
- A deduction lowers the income you're taxed on; a credit lowers the tax itself, dollar for dollar. A credit is usually worth more per unit than a deduction.
- Why is my effective rate so much lower than my bracket?
- Because most of your income is taxed in the lower brackets. Only the top slice hits your marginal rate, pulling the average well below it.
- Does this cover social security or payroll taxes?
- No. Income tax and social/payroll contributions are separate levies with their own rules; the brackets here describe income tax only.
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