Income and career · Calculator

Maxing your 401(k)
changes your take-home pay.

Pre-tax contributions reduce your taxable income. Enter your salary to see how maximizing each account affects your take-home pay.

The question it answersHow much does maxing my 401(k) actually cost me in take-home pay?

Rules: United States. Tax year: models 2026 figures; check the assumptions before using it for another year. Privacy: runs in your browser. What you enter stays on your device unless you copy a share link, which puts your inputs in the link.

// VERIFY NUMBERS FICAFederal Insurance Contributions Act (FICA)The federal payroll tax that funds Social Security and Medicare. Workers pay 6.2% for Social Security (on wages up to $184,500 in 2026) plus 1.45% for Medicare, and employers match both. Self-employed people pay both halves, 15.3%, as self-employment tax.Full definition caps, federal-tax brackets, and 401(k)/HSAHealth Savings Account (HSA)A health savings account available only when eligibility requirements are met. Federal tax benefits depend on contribution limits and qualified medical expenses. Health coverage, other coverage and Medicare enrollment can affect eligibility; state tax treatment can differ.Full definition contribution limits update every January. Figures baked into this tool reflect the year noted in the source; verify the current year's numbers at irs.gov and ssa.gov before treating a result as final.
CURRENT ELECTIONS ($/YEAR)
OPTIMIZE TO 2026 MAX ×DON'T TRUST, VERIFYClaim: 2026 contribution limits: 401(k) $24,500, HSA $4,400/$8,750, FSA $3,400.Verify at: IRS 2026 401(k) limit announcement ↗ Source 2 in the list belowIndexed annually for inflation. HSA limits: IRS Rev. Proc. 2025-19; FSA limit: IRS Rev. Proc. 2025-32. Both are linked in the sources under How this is calculated.
KEY INSIGHT
CURRENT SETUP
OPTIMIZED SETUP

FICA note: Social Security and Medicare taxes (FICA, 7.65% combined employee share, with Social Security's 6.2% stopping at the $184,500 wage base) apply to your full gross salary minus payroll HSA and FSA contributions. Wages above $200,000 ($250,000 married filing jointly) owe an extra 0.9% Medicare tax, which the tool includes. 401(k) contributions reduce federal and state income tax but not FICA; payroll HSA contributions reduce all three ×DON'T TRUST, VERIFYClaim: FICA is 7.65% employee share (6.2% SS + 1.45% Medicare). HSA via payroll avoids FICA; 401(k) does not.Verify at: IRS Topic 751 ↗ Source 3 in the list belowSocial Security tax applies up to the annual wage base; Medicare has no cap..

Estimate, not tax or legal advice. It applies the 2026 rules listed in the assumptions to the numbers you enter. Details this tool does not model can change the result.

What this tool assumes
  • Federal income tax is the full-year 2026 liability from the brackets and the standard deduction, spread evenly across paychecks. It is not W-4 or Publication 15-T withholding, so the amount actually withheld from each check can differ.
  • Social Security tax is 6.2% of wages up to the 2026 wage base ($184,500). Medicare tax is 1.45% of all wages, plus the 0.9% Additional Medicare Tax on wages above $200,000 (single, head of household) or $250,000 (married filing jointly).
  • Married filing jointly treats the salary entered as the household's only wages. Employers start withholding the 0.9% at $200,000 regardless of filing status, so a joint filer earning $200,000 to $250,000 sees it withheld and gets it back when filing.
  • State tax estimated using the flat rate you enter. A rate above 100% is not valid, so 100% is used and the result says so.
  • A checked maximum raises that account to its 2026 limit and never lowers it. A current amount above the limit (for example a 401(k) that includes an age-50 catch-up) is kept as entered, and the result says so.
  • A checked maximum never pushes take-home below zero: on a low salary the checked amounts are trimmed (401(k) first, then HSA, then FSA) to what the paycheck can fund, but never below your current election for that account. If your current elections alone leave take-home below zero, the tool says so and adds nothing.
  • Only one HSA maximum, self-only or family, can apply: checking one clears the other. If a saved state or shared link has both checked, the self-only maximum is used, the family box is cleared, and the result says so.
  • Negative entries are treated as zero, and the result names the field.

Not financial advice. Rough estimates for standard deductionstandard deductionA fixed dollar amount that reduces your taxable income without itemizing. Most people claim this instead of listing individual deductions.Full definition filers. Actual tax situations vary.

HOW THIS IS CALCULATED

This tool runs entirely in your browser: no data is sent to any server. The 2026 tax figures are fixed numbers in the page code.

  • The calculation runs twice: once with your current 401(k), HSA and FSA amounts, and once with each checked box raised to its 2026 limit: 401(k) $24,500[2], HSA $4,400 self-only or $8,750 family[4], health FSA $3,400[5]. A checked box never lowers an election: a current amount already above the limit is kept as entered, and the result says so. Catch-up contributions are not included. If those maximums would leave take-home below zero, the checked amounts are reduced (401(k) first, then HSA, then FSA) until take-home is exactly zero; a reduced amount never goes below your current election for that account. If your current elections alone leave take-home below zero, both columns show that negative figure and the result asks you to lower them.
  • Federal taxable income = salary minus 401(k), HSA and FSA minus the 2026 standard deduction: $16,100 single, $32,200 joint, $24,150 head of household[5][6]. Tax is applied bracket by bracket from 10% to 37% at the 2026 thresholds; for single filers the bracket tops are $12,400, $50,400, $105,700, $201,775, $256,225 and $640,600[5].
  • State tax = (salary minus all three contributions) × the rate you enter, with no state deduction. A rate above 100% is not valid; 100% is used and the result says so.
  • FICA = 6.2% of (salary minus HSA and FSA) up to $184,500, plus 1.45% of the same base with no cap[3], plus 0.9% of that base above $200,000 (single, head of household) or $250,000 (married filing jointly)[7]. 401(k) deferrals do not lower it.
  • Take-home = salary minus contributions minus federal, state and FICA. Per paycheck = annual ÷ 52, 26, 24 or 12.
  • Tax saved = current total tax minus optimized total tax; the take-home drop is current take-home minus optimized take-home. The two add up to the extra contribution, so the tax saved shown is the rounded extra contribution minus the rounded take-home drop, which keeps the three dollar figures consistent.

Federal tax is the annual liability spread evenly across paychecks, not the W-4 withholding formula. Not modeled: a spouse's wages, tax credits, itemized deductions, states that tax HSA contributions, and employer contributions. Verify the methodology or inspect the source code in your browser's dev tools.

Where to go from here

Read next

Order of Operations

The order to deploy each dollar: emergency fund, employer match, high-interest debt, HSA, Roth, then taxable.

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Sources

Bracketed numbers and verify badges in the text link to these sources. Figures, rates and rules change: check each source’s date before acting on it.

  1. Tax Foundation, Tax Foundation state rates ↩
  2. Internal Revenue Service, 401(k) limit increases to $24,500 for 2026, IRA limit increases to $7,500. Checked 2026-09-26. ↩
  3. Internal Revenue Service, Topic no. 751, Social Security and Medicare withholding rates. Checked 2026-09-26. ↩
  4. Internal Revenue Service, Rev. Proc. 2025-19 (2026 HSA limits). Checked 2026-09-26. ↩
  5. Internal Revenue Service, IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill. Checked 2026-09-26. ↩
  6. Internal Revenue Service, Rev. Proc. 2025-32 (2026 inflation adjustments). Checked 2026-09-26. ↩
  7. Internal Revenue Service, Topic no. 560, Additional Medicare tax. Checked 2026-09-26. ↩
  8. Internal Revenue Service, IRS limit announcements

Calculators are educational estimates, not financial advice. Disclosures · How pages are reviewed