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RETIREMENT · 2026

401k Paycheck Impact Calculator — What It Really Costs

Raising your contribution never costs you the full amount. This 401k paycheck impact calculator puts the two numbers side by side: how much more goes into your retirement account, and how much smaller your actual deposit gets. Pick your salary, state and pay frequency, and it works out the gap — plus the employer match you may be leaving behind.

401(k) Paycheck Impact
What raising your contribution really costs
% of pay
% of pay
% of what you put in
% of pay
Take-home pay falls by this much per paycheck
$139.73
…to put $201.92 more into your 401(k). Every extra dollar saved costs you $0.69 of take-home pay.
Take-home now$2,147.70
Take-home after the change$2,007.97
Your contribution per paycheck$288.46
Employer match per paycheck$86.54
Federal and state tax saved per paycheck$62.19
Your contributions this year$7,500
Total into the account this year$9,750

Traditional pre-tax contributions only. They reduce federal and most state income tax but not Social Security or Medicare, which is why take-home falls by less than you contribute but by more than nothing. Roth 401(k) contributions come out of after-tax pay, so there your take-home falls by the full amount. Pennsylvania and a few other states tax contributions when they are made rather than when they are withdrawn.

THE CORE IDEA

Why a $200 401k Contribution Only Costs About $150 of Take-Home Pay

A traditional 401(k) contribution is taken from your pay before federal and state income tax are calculated. Deferring another $200 a paycheck lowers the wage those taxes are computed on by $200, so the tax withheld falls too. The money that would have gone to the IRS goes into your account instead, and your take-home pay drops by only the remainder.

How much remainder depends entirely on your marginal rate. Someone at 12% federal in a no-income-tax state sees take-home fall by about $176 of that $200. Someone at 24% federal in California sees it fall by roughly $130. That spread is why a single rule of thumb is useless here, and why this 401k paycheck impact calculator asks for your state and filing status before it gives you a number.

THE PART PEOPLE MISS

Your 401k Does Not Shrink FICA, However Much You Defer

Social Security and Medicare are calculated on your full gross pay. Elective deferrals are exempt from income tax but not from FICA, so contributing more does nothing at all to the 6.2% and 1.45% lines on your stub.

This catches people who expect their take-home to fall by only the income-tax-adjusted amount and find it falls by more. It also means the effective discount on a 401(k) contribution is your income-tax rate alone — not your total payroll-tax burden. The calculator above models FICA on gross, which is why its figure is lower than the back-of-envelope version you may have run.

THE MATCH

The Employer Match Is the Only Guaranteed Return on a 401k

Most matching formulas look like “50% of what you contribute, up to 6% of pay” or “100% up to 4%”. Contribute below that ceiling and the unmatched portion is not deferred to later or paid another way — it is simply never paid. On a $75,000 salary, contributing 3% instead of 6% under a 50%-to-6% formula leaves about $1,125 a year on the table.

Enter your employer’s formula above and the calculator warns you when your contribution is below the match limit, and shows the match as a per-paycheck figure beside your own contribution. Whatever else you decide about retirement saving, the stretch from your current rate up to the match limit is the part with a defined, immediate return.

TIMING

Hitting the 401k Limit Early Changes Your Last Paychecks

The 2026 elective deferral limit is $24,500, plus an $8,000 catch-up from age 50. If your contribution rate would take you past it, payroll normally stops deferring once you reach the cap — so your final paychecks of the year arrive noticeably larger than the earlier ones, with no 401(k) line at all.

That is worth planning around for two reasons. Some employers only match on paychecks where you actually contribute, so front-loading contributions early in the year can cost you match on the periods after you stop — plans with a “true-up” provision fix this at year end, and plans without one do not. And a change made in autumn has fewer remaining paychecks to work through, so the per-paycheck impact of the same annual target is larger the later you leave it.

FAQ

401k Paycheck Impact Calculator — Frequently Asked Questions

How much will a 401(k) contribution reduce my paycheck?+

By less than you contribute. A traditional 401(k) deferral comes out of pre-tax wages, so it reduces the income your federal and state withholding are calculated on. Someone in a combined 22% federal and 5% state position sees take-home fall by roughly 73 cents for every dollar deferred. The calculator above works out the exact figure for your salary, state and filing status.

Does a 401(k) contribution reduce Social Security and Medicare tax?+

No. This is the single most common misunderstanding about 401(k) contributions. Elective deferrals are exempt from federal and most state income tax but not from FICA — Social Security and Medicare are calculated on your full gross pay. It is why your take-home falls by less than your contribution but by more than your income-tax saving alone would suggest.

How much should I contribute to get the full employer match?+

At least up to the percentage your employer matches. A common formula is 50% of what you put in, up to 6% of pay — contribute 6% and the employer adds 3%, contribute 4% and they add 2%, and the other 2% of matched money is simply not paid. Enter your employer's formula above and the calculator flags it when your contribution is below the match limit.

What is the 401(k) contribution limit for 2026?+

The elective deferral limit is $24,500, with an additional $8,000 catch-up for those aged 50 and over. The limit applies to what you defer from salary, not to employer matching contributions, which sit under a separate and much higher combined cap. Payroll normally stops your deferrals once you reach the limit, which makes your final paychecks of the year larger.

Is a Roth 401(k) different on my paycheck?+

Yes, and the difference is the whole point of this tool. Roth contributions come out of after-tax pay, so your take-home falls by the full amount you contribute — there is no immediate tax saving. The trade is that qualified withdrawals in retirement are tax free. The calculator above models traditional pre-tax contributions.

Do all states give a tax break on 401(k) contributions?+

Most do, but not all. Pennsylvania taxes elective deferrals when they are made rather than when they are withdrawn, so a Pennsylvania worker sees no state-tax reduction from contributing. In the nine states with no wage income tax there is nothing to reduce, so the whole saving is federal. Selecting your state above accounts for this.

Should I increase my 401(k) if money is tight?+

This calculator answers the arithmetic question, not the financial-planning one, and the arithmetic usually looks better than people expect because of the pre-tax effect and the match. Whether that makes raising your contribution the right call depends on your debts, emergency savings and plan options — a licensed adviser is the right person for that question.

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