To calculate your effective tax rate, divide your total federal tax by your income and multiply by 100. On a completed Form 1040, that means taking the total tax on Line 24 and dividing it by either your total income (Line 9) or your taxable income (Line 15). If you owed $8,000 in federal tax on $65,000 of income, your effective tax rate is 12.3 percent. The arithmetic is simple. The judgment call is which income figure to put in the denominator, and what to do about credits and payroll taxes that the basic formula doesn’t capture.
The Formula
Every effective tax rate calculation is the same fraction:
Effective Tax Rate = (Total Tax ÷ Income) × 100
The numerator is your federal tax liability. The denominator is an income figure you choose based on what you want the number to tell you. Multiply the decimal result by 100 to express it as a percentage, and carry at least two decimal places before rounding so year-over-year comparisons stay clean.
Pick Your Income Base
The denominator shapes the answer. Two choices are standard.
Total income sits on Line 9 of Form 1040 and captures every dollar you earned before any adjustments or deductions. This produces the broadest ETR and answers the question, “What share of everything I made went to federal tax?”
Taxable income sits on Line 15, after subtracting above-the-line adjustments and either the standard or itemized deduction. For 2026, the standard deduction is $16,100 for single filers and $32,200 for married couples filing jointly.1Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments From the One, Big, Beautiful Bill Because the denominator is smaller, this version produces a higher percentage. It shows how the tax code treated the income actually subject to tax.
Neither is wrong. Running both reveals exactly how much your deductions moved the needle. Adjusted gross income on Line 11 is a reasonable middle-ground denominator if you want something between the two.
Find the Numbers on Form 1040
Everything you need is on your completed return.2Internal Revenue Service. About Form 1040, U.S. Individual Income Tax Return
- Line 9 — Total income. All income before adjustments. Use this for a broad-picture ETR.
- Line 11 — Adjusted gross income. Total income minus above-the-line deductions like student loan interest and retirement contributions.
- Line 15 — Taxable income. AGI minus the standard or itemized deduction. Use this for a narrower ETR focused on the income actually subject to tax.
- Line 16 — Tax. The initial tax from the tax tables, before credits.
- Line 24 — Total tax. Your actual liability after non-refundable credits and after additional taxes like self-employment tax and the Additional Medicare Tax. This is your numerator.
Use Line 24, not Line 16. Line 24 is the closest single figure to your true federal tax cost for the year.
A Worked Example
Suppose you’re a single filer with $75,000 in total income on Line 9. After the $16,100 standard deduction, your taxable income on Line 15 is $58,900. Your total tax on Line 24 comes to $8,420. The two calculations:
- Using total income: $8,420 ÷ $75,000 = 0.1123 × 100 = 11.23%
- Using taxable income: $8,420 ÷ $58,900 = 0.1430 × 100 = 14.30%
The gap between those two percentages is entirely the effect of your deduction. Both numbers are correct; they answer different questions.
Effective Rate vs. Marginal Rate
These get confused constantly, and the confusion drives bad financial decisions. Your marginal rate is the percentage applied to your last dollar of taxable income. Your effective rate is the blended average across all your income. They can differ by ten percentage points or more.
For 2026, a single filer with $105,700 in taxable income sits in the 24 percent bracket.1Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments From the One, Big, Beautiful Bill But the first $12,400 was taxed at 10 percent, the next chunk at 12 percent, and so on. The actual tax owed is about $17,966, which works out to an effective rate of roughly 17 percent on taxable income, not 24.3Internal Revenue Service. Revenue Procedure 2025-32
This distinction matters when you’re evaluating extra income. A freelancer in the 24 percent bracket who turns down a $5,000 project because “taxes would eat it” is leaving $3,800 after tax on the table. Marginal tells you the cost of the next dollar. Effective tells you the average cost of all your dollars. Use marginal for forward-looking decisions and effective for backward-looking assessments of your total burden.
How Credits Change the Numerator
Credits reduce your tax bill dollar for dollar, which shrinks your ETR. The two types of credits behave differently in the calculation.
Non-refundable credits, like the Child and Dependent Care Credit, can reduce your tax to zero but no further. If you owe $1,500 and have a $2,000 non-refundable credit, the extra $500 is lost. These credits are already reflected in Line 24, so they lower your ETR automatically.
Refundable credits, like the Earned Income Tax Credit, can push your liability below zero and generate a refund.4Internal Revenue Service. Earned Income Tax Credit (EITC) The refundable portion appears later on the return (around Line 33) and is not included in Line 24. If you receive substantial refundable credits, your true after-credit federal burden may be lower than Line 24 suggests, or even negative. To capture that in your ETR, subtract the refundable credit from your Line 24 total before dividing. Otherwise Line 24 accounts for everything except those refundable portions.
Adding Payroll Taxes for a Fuller Picture
The basic formula only covers income tax. For most workers, payroll taxes take a meaningful additional bite. Including them gives you a more honest measure of your total federal tax burden.
For 2026, Social Security tax is 6.2 percent on wages up to $184,500, and Medicare tax is 1.45 percent on all wages with no cap.5EY Tax News Update. Social Security Wage Base to Increase in 2026 High earners also pay an additional 0.9 percent Medicare tax on earnings above $200,000 for single filers or $250,000 for joint filers.6Internal Revenue Service. Topic No. 560, Additional Medicare Tax
To calculate an all-in federal ETR, add the employee’s share of Social Security and Medicare (visible on your W-2) to your Line 24 total, then divide by total income. For someone earning $75,000, that adds roughly $5,738 in payroll taxes to the numerator, which is enough to push a seemingly modest 11 percent income-tax ETR into the mid-to-high teens. Self-employed taxpayers pay both the employee and employer shares, so their payroll tax impact is roughly double.
Adding State Tax
Your federal ETR is only part of the picture. State income tax rates range from zero in states without an income tax to more than 13 percent at the top end. Add your state income tax liability to the numerator alongside your federal total, then divide by income. The formula is the same; you’re just combining both amounts before dividing.
Because state structures vary widely, a combined ETR can shift by several percentage points if you move, which is worth modeling before any relocation.
One Caveat on Investment Income and Other Add-Ons
If a meaningful share of your income comes from long-term capital gains or qualified dividends, those are taxed at preferential rates of 0, 15, or 20 percent depending on your taxable income, which tends to pull an investment-heavy filer’s ETR below what a pure wage earner at the same income would pay.7Tax Foundation. 2026 Tax Brackets and Federal Income Tax Rates Extra layers such as the Net Investment Income Tax and the Alternative Minimum Tax can push liability the other way.8Internal Revenue Service. Topic No. 559, Net Investment Income Tax Both are already folded into your Line 24 total, so the standard formula still works without adjustment. If your ETR jumps year over year and your income didn’t, those are the first places to look.