What is Federal Income Tax Estimator (2026)?
Free Form 1040 federal income tax estimator using 2025 IRS brackets (Rev. Proc. 2024-40), standard deduction, Child Tax Credit (IRC § 24), SE tax, LTCG with proper stacking, and NIIT. All 5 filing statuses. No signup required.
Federal Income Tax runs entirely in your browser using JavaScript (browser). Your data never leaves your device.
Free Federal Income Tax Estimator (2026)
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.
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
$9,214
Effective rate: 11.5% · Marginal: 22%
You owe
$9,214
Effective 11.5% · marginal 22%
Owe
$9,214
Total tax
$9,214
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: $15,000 single, $30,000 MFJ, $22,500 HoH (Rev. Proc. 2024-40 § 3.18).
- Ordinary income tax via bracket walk using the 2025 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.
- 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 ($2,000 per child under 17 per IRC § 24, 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.
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, 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 $10k) + 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.
- 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). 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: $15,000 single, $30,000 MFJ, $22,500 HoH. Itemize if your total of (a) mortgage interest, (b) state and local taxes capped at $10k under TCJA, (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 $2,000 per qualifying child under 17 (IRC § 24). Phases out at $200k AGI single / $400k MFJ by $50 per $1,000 of excess. Of the $2,000, 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 remaining $300 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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