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Free Federal Income Tax Calculator
Get a full Form 1040 federal tax estimate without leaving the browser. Wages + SE income + interest/dividends + short-term and long-term capital gains; pre-tax 401(k)/IRA/HSA adjustments; standard or itemized deduction; Child Tax Credit with $200k/$400k phase-out; LTCG taxed at preferential rates with proper bracket stacking; SE tax via Schedule SE; NIIT 3.8% for high earners. Marginal vs effective rate, refund or owed estimate.
Use 2026 for current-year planning; switch to 2025 for the return you file in early 2026.
You
For Child Tax Credit ($2,000 each, phases out above $200k single / $400k MFJ).
Income
Adjustments (above-the-line)
Deduction
Withholding (for refund/owed)
From your W-2 box 2 + 1099 withholding + estimated payments.
You owe
$8,770
Effective rate: 11.0% · Marginal: 22%
You owe
$8,770
Effective 11.0% · marginal 22%
Owe
$8,770
Total tax
$8,770
📐 Open methodology, sources & limitations
Formula
Total income = wages + SE income + interest/dividends + short-term gains + long-term gains AGI = total income − (half of SE tax + traditional 401(k) + traditional IRA + HSA) Deduction = standard deduction (selected year, by filing status) OR itemized amount Taxable income = max(0, AGI − deduction) Ordinary taxable = max(0, taxable income − long-term gains) Ordinary tax = bracket walk(ordinary taxable, selected-year brackets) (IRC §1) LTCG tax = preferential 0/15/20% on long-term gains stacked on ordinary taxable (IRC §1(h)) SE tax = Schedule SE: 92.35% × (12.4% to SS wage base + 2.9% Medicare + 0.9% add'l) NIIT = 3.8% × min(investment income, AGI − threshold) (IRC §1411) Tax before credits = ordinary tax + LTCG tax + SE tax + NIIT Child Tax Credit = $2,200 × children under 17, less $50 per $1,000 of AGI over $200k/$400k Tax after credits = max(0, tax before credits − credits) Refund or owed = federal withholding − tax after credits
Assumptions
- Federal brackets (10/12/22/24/32/35/37%) and standard deduction follow the selected tax year. 2025 standard deduction (post-OBBBA): $15,750 single, $31,500 MFJ, $23,625 HoH. 2026: $16,100 single, $32,200 MFJ, $24,150 HoH.
- Long-term capital gains and qualified dividends are taxed at preferential 0/15/20% rates, stacked on top of ordinary taxable income.
- Above-the-line adjustments modeled: half of SE tax, traditional 401(k), traditional IRA, and HSA contributions.
- Child Tax Credit is $2,200 per qualifying child under 17 (OBBBA), phasing out by $50 per $1,000 of AGI above $200,000 single / $400,000 MFJ.
- Net Investment Income Tax of 3.8% applies to investment income when AGI exceeds $200,000 single / $250,000 MFJ.
Sources
- IRC §1 — Tax imposed (ordinary income brackets) — §1
- IRC §1(h) — Maximum capital gains rate (0/15/20%) — §1(h)
- IRC §24 — Child Tax Credit — §24
- IRC §164(f) — Deduction for one-half of self-employment tax — §164(f)
- IRC §1411 — Net Investment Income Tax — §1411
- IRS Rev. Proc. 2024-40 — 2025 inflation-adjusted brackets, as modified by OBBBA (July 4, 2025) — §3.18
- IRS Rev. Proc. 2025-32 — 2026 inflation-adjusted brackets and standard deduction — §3.01, §3.18
This tool does NOT model:
- Alternative Minimum Tax (IRC §55)
- State and local income tax
- Earned Income Tax Credit, education credits, and the saver’s credit
- Foreign tax credit
- Traditional IRA deduction AGI phase-outs
- Roth conversion math and business-entity (S-corp / partnership) flow-through complexities
Last reviewed: 2026-06-12 · Tax year modeled: 2025 & 2026 (selectable)
This methodology section exists so you can verify the math. We show our formulas because you deserve to know how a number was calculated. This is calculation transparency, not financial advice.
What changed for 2026
The 2026 figures come from IRS Rev. Proc. 2025-32, the first full inflation adjustment after the One Big Beautiful Bill Act (OBBBA, July 4, 2025). The seven bracket rates are unchanged, but every bracket threshold and the standard deduction moved up. The OBBBA changes already in effect for 2025 carry into 2026: the Child Tax Credit stays at $2,200 per child, and the SALT itemized-deduction cap stays at $40,000. Use the year toggle in the calculator above to compare your bill under both years.
| Figure | 2025 | 2026 |
|---|---|---|
| Standard deduction — single | $15,750 | $16,100 |
| Standard deduction — married filing jointly | $31,500 | $32,200 |
| Standard deduction — head of household | $23,625 | $24,150 |
| Top of 22% bracket — single | $103,350 | $105,700 |
| Child Tax Credit (OBBBA) | $2,200 | $2,200 |
How federal income tax actually works
Your federal tax bill is computed in a specific sequence that this calculator mirrors:
- Total income = wages + self-employment + interest + dividends + capital gains (short + long).
- AGI (Adjusted Gross Income) = total income − above-the-line adjustments. Adjustments include: half of self-employment tax (IRC § 164(f)), traditional 401(k) contributions (§ 402(g)), deductible IRA (§ 219), HSA (§ 223). AGI determines eligibility for many credits and phase-outs.
- Taxable income = AGI − standard or itemized deduction. 2025 standard deduction (post-OBBBA): $15,750 single, $31,500 MFJ, $23,625 HoH. For 2026: $16,100, $32,200, and $24,150 (Rev. Proc. 2025-32).
- Ordinary income tax via bracket walk using the selected year's rates (10/12/22/24/32/35/37%). LTCG/qualified dividends excluded from this calculation — they get their own bracket schedule.
- LTCG tax at preferential rates (0/15/20%) under IRC § 1(h), with LTCG stacking on top of ordinary taxable income for bracket placement. To model a specific sale, use the capital gains tax calculator.
- SE tax per Schedule SE: 15.3% × (net SE × 92.35%) with SS wage base + Medicare uncapped + Additional Medicare above $200k/$250k.
- NIIT at 3.8% on investment income for high-AGI filers (above $200k single / $250k MFJ, IRC § 1411).
- Subtract credits: Child Tax Credit ($2,200 per child under 17 per IRC § 24 as amended by OBBBA, phasing out above $200k/$400k AGI), plus other credits this calculator doesn't model (EITC, education, saver's, foreign tax, etc.).
- Compare to withholding to compute refund or amount owed. To estimate the withholding side per pay period, use the paycheck calculator.
Marginal vs effective rate
Your marginal rate is the rate that applies to your NEXT dollar of income — useful for planning decisions like "should I make this Roth conversion?" or "is this freelance gig worth the tax bite?" Your effective rate is total tax ÷ total income — what you actually paid as a percentage. The effective rate is always lower than the marginal rate because lower-income brackets are below your marginal one. For a single filer with $100k taxable income in 2025, marginal is 22% but effective is closer to 17% (~$16,914 ÷ $100,000).
Common federal income tax mistakes
- Confusing AGI with taxable income. AGI includes deductions for above-the-line items (401k, IRA, HSA, half SE tax). Taxable income further subtracts the standard or itemized deduction. The IRS uses both numbers for different thresholds — AGI for credits, taxable income for tax computation.
- Itemizing when standard wins. Since TCJA 2017, the standard deduction doubled and most filers now take it. Itemize only if your mortgage interest + SALT (capped at $40,000 under OBBBA, up from $10,000) + charitable + medical (over 7.5% AGI) exceeds the standard deduction.
- Missing the Child Tax Credit phase-out. Above $200k single / $400k MFJ AGI, CTC phases out by $50 per $1,000 of excess income. A $250k AGI single filer with 2 kids loses $2,500 of the $4,000 credit.
- Forgetting that LTCG stacks above ordinary income. LTCG bracket placement depends on TOTAL stacked income, not LTCG alone. A retiree with $30k ordinary income and $40k LTCG falls entirely in the 0% LTCG bracket (below $48,350); the same $40k LTCG with $80k of wages instead puts the LTCG entirely in 15%.
- Underestimating SE tax. Self-employment tax (15.3% × 92.35%) is on top of income tax. A 1099-only person at $80k owes both — total federal tax ~26% effective, not just the income tax rate. The self-employment tax calculator breaks down that piece.
- Not maxing tax-advantaged accounts. Traditional 401(k) ($23,500), HSA ($4,300 single / $8,550 family), Traditional IRA ($7,000) all reduce AGI dollar-for-dollar. At 24% bracket, maxing all three saves ~$8,500 in federal tax.
Frequently Asked Questions
How do federal tax brackets work?+
Brackets are marginal — each rate applies only to the income within that bracket's range. For 2025 single: 10% to $11,925, 12% to $48,475, 22% to $103,350, 24% to $197,300, 32% to $250,525, 35% to $626,350, 37% above (Rev. Proc. 2024-40 § 3.01). Toggle the calculator to 2026 for the Rev. Proc. 2025-32 brackets. Your "marginal rate" is the highest bracket your income reaches; your "effective rate" is total tax ÷ income.
Standard deduction or itemize — which is better?+
Take whichever is larger. Standard deduction for 2025 (post-OBBBA): $15,750 single, $31,500 MFJ, $23,625 HoH. For 2026: $16,100 single, $32,200 MFJ, $24,150 HoH (Rev. Proc. 2025-32). Itemize if your total of (a) mortgage interest, (b) state and local taxes capped at $40,000 under the OBBBA (up from the $10k TCJA cap), (c) charitable contributions, and (d) medical expenses above 7.5% of AGI exceeds the standard deduction. Most filers (~85% post-TCJA) take the standard.
What's the difference between AGI and taxable income?+
AGI (Adjusted Gross Income) = total income minus above-the-line adjustments (401k, IRA, HSA, half-of-SE-tax). It's used to qualify for credits and phase-outs. Taxable income = AGI minus the standard or itemized deduction. It's the actual base for computing income tax.
How is LTCG taxed when I also have ordinary income?+
LTCG is taxed at preferential 0/15/20% rates under IRC § 1(h), but the brackets are determined by your TOTAL income (ordinary + LTCG stacked). If you have $50k ordinary and $30k LTCG as a single filer, the $30k LTCG falls above the $48,350 zero-bracket cap (since $50k already exceeds it), so it's all taxed at 15%. Lower ordinary income would push some LTCG into the 0% bracket.
What's the Child Tax Credit?+
Up to $2,200 per qualifying child under 17 (IRC § 24, as increased by the OBBBA). Phases out at $200k AGI single / $400k MFJ by $50 per $1,000 of excess. Of the $2,200, up to $1,700 is refundable (the "Additional Child Tax Credit") meaning you can get it as a refund even if your tax owed is zero. The remainder is non-refundable. (Note: this calculator simplifies by treating CTC as fully credit-eligible against tax owed.)
Why does my SE income owe more tax than W-2 income?+
Self-employment income owes Schedule SE tax (15.3% × 92.35% = ~14.13%) ON TOP of regular income tax. A W-2 employee pays only their half (7.65%); their employer pays the matching 7.65%. As a freelancer, you pay both halves. Result: 1099 income at $80k owes ~$11k SE tax plus ~$10k income tax = ~$21k total federal tax, vs ~$10k for the same W-2 wages.
When does NIIT apply?+
Per IRC § 1411, an additional 3.8% applies to investment income (interest, dividends, capital gains, rental income) when your AGI exceeds $200k single / $250k MFJ / $125k MFS. The 3.8% applies to the LESSER of (a) net investment income or (b) AGI over the threshold. Thresholds are set by statute — not inflation-adjusted.
Is my data stored?+
No. All math runs entirely in your browser. Your income, deductions, and dependents never touch any server.
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