Enter your gross pay, how often you are paid, your pre-tax retirement contribution as a percentage, your annual pre-tax health premium, and your best estimate of your effective federal and California income tax rates. The tool estimates each payroll deduction and your take-home per period — then, most importantly, shows what your retirement contribution actually costs you in take-home, which is always less than the amount you contribute.
Why this tool asks for your tax rates instead of guessing them. Federal and California income tax brackets, standard deductions and thresholds change every single year. A calculator with last year's brackets baked in gives you a confidently wrong answer and never tells you it is out of date. So we ask you for two numbers instead. Your effective rate is total income tax divided by income — not your top bracket, and usually a good deal lower. The fastest source is last year's tax return: divide your total tax by your total income. Otherwise, estimate from the current tables at irs.gov (federal) and ftb.ca.gov (California). If you are unsure, try a range — the retirement-contribution insight below holds across all of them.
Your pay
Estimated, per paycheck
What the retirement contribution actually costs you
That last block is the whole point of this page. A pre-tax contribution comes out of your pay before federal and California income tax are calculated, so the government funds part of it. The higher your rates, the more of your contribution the tax deferral covers — and the smaller the hole in your paycheck. It is not free money and it is not a tax cut: the tax is deferred, not forgiven, and you will pay it on withdrawal. But the paycheck arithmetic is real, and it is the reason "I cannot afford to contribute" is worth testing before it is believed.
Assumptions used — read these before trusting the number
- Income tax is your rate, applied flat. Federal and California income tax are estimated as your effective rate multiplied by pay after pre-tax deductions. Real withholding uses graduated brackets, your Form W-4 entries, the standard or itemised deduction, credits, and other household income. This tool applies no brackets at all — by design, so that it cannot silently go out of date. Verify against IRS Publication 15-T and the FTB withholding schedules.
- Social Security: 6.2% up to the annual wage base. The wage base used here is $184,500, the 2026 contribution and benefit base, and it is printed in the results note below. Earnings above it are not subject to the 6.2%. Source: SSA — Contribution and benefit base.
- Medicare: 1.45% on all wages, plus an additional 0.9% on wages above $200,000 single, $250,000 married filing jointly, $125,000 married filing separately and $200,000 head of household. These thresholds are set in statute and are not indexed for inflation. Employers withhold the additional amount based on wages from that employer alone, so your return may true it up in either direction. Source: IRC § 3101(b)(2).
- California SDI is applied at an illustrative rate — this one figure is not yet confirmed for the current year. The rate is set by the state and has changed repeatedly in recent years, including changes to whether a wage cap applies at all.
- Pre-tax health premiums reduce income tax and payroll tax; pre-tax retirement contributions reduce income tax only. Section 125 health premiums are generally exempt from Social Security and Medicare, while 401(k)-type deferrals are not — which is why contributing more to your 401(k) does not reduce your FICA. This distinction is modelled.
- Excluded entirely: employer match (which is real money and not in your paycheck), HSA and FSA contributions, after-tax and Roth deferrals, wage garnishments, union dues, local taxes, supplemental withholding on bonuses, and any state other than California.
- Contribution limits are not enforced. Entering a percentage that would exceed the annual elective deferral limit will still compute. For 2026 that limit is $24,500, with an $8,000 catch-up at age 50 and over and $11,250 at ages 60 to 63. Source: IRS Notice 2025-67.
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This is an estimate, not advice. The output above is arithmetic performed on the numbers you entered, under the assumptions printed on this page. It is not a recommendation, not a projection you should rely on, and not a substitute for a conversation with your CPA or a qualified adviser about your own situation.
Common questions
Common questions
Why does my contribution reduce my take-home by less than I contribute?
Because the contribution comes out before income tax is calculated. If your combined federal and California effective rate is 13%, then roughly 13 cents of every dollar you defer would have gone to tax anyway — so your paycheck only falls by about 87 cents. Payroll taxes still apply to the deferral, which is why the saving tracks your income tax rates and not your whole tax burden.
Is this the same as a paycheck calculator from a payroll company?
No, and deliberately so. Payroll calculators bake in a specific year's brackets and W-4 logic, which makes them precise until the law changes and quietly wrong afterwards. This one asks you for your effective rates so the arithmetic stays honest, and tells you plainly where it is approximating. Your actual withholding comes from your employer applying IRS Publication 15-T and the FTB schedules to your W-4 and DE 4.
Should I contribute pre-tax or Roth?
This tool models pre-tax only. Roth contributions come out after tax, so they reduce your take-home by the full amount — but they grow and come out tax-free. Which is better depends on your tax rate now versus in retirement, the same trade our Roth conversion estimator lays out. Our guide covers the choice.
My employer offers a match. Where is it?
Not here — a match does not appear in your take-home, it appears in your account. It is also the highest-return item in most people's financial lives: an immediate, guaranteed addition to your savings for money you were going to set aside anyway. If you are contributing less than the full match, that is usually the first thing to fix.
Not sure what you can actually afford to save?
That is a fifteen-minute conversation, not a spreadsheet problem. We will look at your paycheck, your match, your debts and your goals — fee-only, $0 to open and $50 a month ongoing, nothing to sell you.