Income tax feels opaque until you see it as slicing a pie: each layer of income is taxed at its own rate, and only the top layer gets the headline rate. Understanding that one idea explains most of tax planning.
The progressive slice
Taxable income is divided into brackets. Each bracket taxes only the income within its range, at that range's rate. That's why moving into a higher bracket raises the rate on the new slice — not on everything you already earned.
Effective vs marginal
Effective rate is your average: total tax over total income. Marginal rate is the tax on your next dollar. Raises, bonuses and extra side income are all priced at the marginal rate — the number that should drive your decisions about earning more.
What this estimate leaves out
A real return subtracts credits, adjusts for state tax and adds many deductions. This calculator is for understanding the mechanics and estimating the ballpark — for filing, professional tools and advice are essential.
Frequently asked questions
After your deduction, income is taxed in progressive slices — each bracket applies only to the income within its range. This calculator sums those slices into your estimated tax.
The effective rate is total tax divided by income — your average rate. The marginal rate is what the next dollar you earn gets taxed at — the one that matters for raises.
No — a common myth. Only the income above each bracket's threshold is taxed at that bracket's rate, so your effective rate is always lower than your marginal rate.