Income Tax Explained: Marginal vs. Effective Rate
The US federal income tax is progressive: you don't pay one rate on everything. Each portion of your income is taxed at the rate for its "bracket." That's why your marginal rate and your effective rate are two different numbers.
Marginal vs. effective — the core distinction
| Term | What it means |
|---|---|
| Marginal rate | The rate on your next dollar of income. This is the "tax bracket" people quote. |
| Effective rate | Your total tax ÷ total taxable income. The real average you actually pay. |
Because only the top slice is taxed at the marginal rate, your effective rate is always lower than your marginal rate (unless all your income sits in the first bracket).
Worked example: $90,000 single filer (illustrative brackets)
Using simplified 2024-style brackets for a single filer, we walk $90,000 of taxable income through the layers:
| Slice of income | Rate | Tax on slice |
|---|---|---|
| First $11,600 | 10% | $1,160 |
| $11,600 – $47,150 | 12% | $4,266 |
| $47,150 – $90,000 | 22% | $9,427 |
| Total tax | — | $14,853 |
- Marginal rate = 22% (the rate on the last dollar)
- Effective rate = $14,853 ÷ $90,000 ≈ 16.5%
So a "22% bracket" taxpayer actually keeps more than 83 cents of most dollars — the 22% only bites the income above $47,150. Bracket fear is usually overstated.
Why the distinction matters
- Taking a raise: extra income is taxed only at the marginal rate on the portion in the higher bracket — you never "lose money" by earning more.
- Deductions: a $1,000 deduction saves you marginal rate × $1,000, not your effective rate.
- Planning: retirement and HSA contributions reduce taxable income at your marginal rate, which is why they're powerful for higher earners.
Frequently asked questions
Are these the exact 2024 IRS brackets?
The example uses rounded, illustrative brackets to teach the mechanism. Dollar amounts and rates change yearly with inflation adjustments — use our income tax estimator for a current-year figure, and confirm with IRS Publication 17 or a tax professional.
Does this include state tax?
No. This is federal only. Most states add their own income tax (a few have none). Your true effective rate is federal plus state plus, where applicable, local taxes.
What about Social Security and Medicare (FICA)?
FICA is a separate payroll tax with its own rates and a wage cap on Social Security. It's not part of the progressive brackets shown here, but it's part of your total tax burden.
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