401(k) Paycheck Impact Calculator
Enter your gross pay, contribution percent, and employer match to see what a Traditional or Roth 401(k) actually costs you per check. The results break out the income tax it saves, any match you are leaving on the table, and where you stand against the 2026 elective deferral limit.
401(k) Paycheck Impact Calculator
Your Paycheck
Your gross for one check, before taxes or 401(k). Paid hourly with a variable check? Use a typical week, or estimate one with the weekly pay estimator.
Your Contribution
The 60 to 63 catch-up is larger, and it applies only in those years. At 64 the standard 50-plus catch-up applies again.
Employer Match
A common formula reads "50% up to 6%": the employer adds 50 cents for every dollar you defer, on the first 6% of your pay.
Tax Situation
A flat estimate you enter yourself. Pick one of the nine no-tax states and this drops to 0.
Estimates only, not tax, legal, or investment advice. Social Security and Medicare are calculated on your full gross either way, because 401(k) deferrals are still FICA wages.
Employer Match
The match never passes through your paycheck. It goes to the plan, so it cannot change any take-home number above.
Annual Deferral Limit
Track the Hours Behind the Paycheck
A percent-of-gross contribution moves with every overtime week and every short week. Download Timeclock44 to log your hours and see the gross that feeds this calculator.
What a 401(k) contribution actually costs your paycheck
A Traditional 401(k) contribution costs you less than the amount you put in, because the money leaves your taxable wages on the way out. Roth is the opposite: it costs the full amount today, and the break arrives at withdrawal instead.
Work through a biweekly example. A single filer grosses $3,000 per check ($78,000 a year), defers 6% Traditional (that is $180 a check, or $4,680 a year), and pays a flat 5% state rate. After the 2026 standard deduction of $16,100, taxable income sits inside the 22% bracket both before and after the deferral, so the $4,680 saves about $1,030 in federal tax. State tax drops another $234. Social Security and Medicare do not move at all. Annual income tax savings come to roughly $1,264, so the $4,680 contribution reduces take-home by about $3,416: near $131 of the $180 per check.
That is the "$1 costs $0.73" framing people search for: at a 22% federal bracket plus 5% state, each dollar deferred costs about 73 cents of take-home. Pick Roth instead and every dollar costs a full dollar right now, because there is no withholding reduction to offset it.
Why your 401(k) does not cut your Social Security and Medicare tax
Elective deferrals are excluded from federal income tax wages, but they remain wages for Social Security, Medicare, and federal unemployment tax. You can verify it on your own W-2: Box 1 (federal taxable wages) will be lower than Box 3 and Box 5 (Social Security and Medicare wages), and the gap is usually exactly your 401(k) for the year.
This is where most quick calculators get it wrong. They subtract the deferral from FICA wages too, which understates the real paycheck hit by about 7.65% of the contribution. The confusion is understandable, because some pre-tax deductions genuinely are FICA-exempt. HSA and FSA contributions do reduce Social Security and Medicare wages, and so do Section 125 health premiums. A 401(k) does not. This calculator computes FICA on your full gross in both scenarios, which is why the tax savings shown here are income tax only.
Employer match, and the money most people leave behind
Match formulas usually read as a rate plus a cap: "50% up to 6%" means the employer adds 50 cents per dollar you defer, on the first 6% of your pay. "100% up to 3%" is a dollar-for-dollar match on a smaller slice. To capture all of it, you contribute at least the cap percent. Contributing more than the cap earns no extra match, though those dollars still get the pre-tax break in a Traditional plan.
The match never appears in your paycheck. It goes into the plan on your behalf, so it does not raise your net pay and it is not withheld from your wages. It also does not count against your elective deferral limit, which caps only your own contributions. A separate Section 415(c) limit covers your money and the employer's money combined, and very few people approach it.
One trap worth checking with HR: if the plan matches per paycheck and you front-load contributions, hitting the annual limit in September stops your deferrals, which stops the match for the rest of the year. Plans with a year-end true-up fix this. Plans without one do not.
Setting a contribution percent when your paycheck changes week to week
Percent-of-gross contributions scale with your gross, which is a feature for hourly workers. An overtime week automatically raises both the dollars deferred and the dollars matched, and a short week lowers both. It also means the "percent needed to max out" figure should be based on realistic annual hours, not a good week, or you will fall short of the limit and be surprised in December.
That calculation only works if you know your real annual gross. Get a realistic hours count first with the annual work hours calculator, then sanity check the per-check figure with the real hourly wage calculator. Both of those lean on an accurate record of what you actually worked. Timeclock44 logs hours per shift and projects pay, so the gross you type into this calculator matches the gross on your stub.
Disclaimer
Estimates only. This calculator uses 2026 federal figures, the standard deduction, and a flat state rate you enter yourself. Your actual paycheck depends on your W-4, your state's real brackets, local taxes, other deductions, and your plan's rules. It is not tax, legal, or investment advice. Check your plan documents and your pay stub.
Frequently Asked Questions
Common questions about 401(k) paycheck impact calculator
How much will contributing to a 401(k) reduce my paycheck?
Less than the amount you contribute, if it is a Traditional (pre-tax) 401(k). The contribution comes out of your taxable wages, so your federal and state income tax withholding drops at the same time. At a 22% federal bracket plus a 5% state rate, $100 contributed cuts your take-home by roughly $73. With a Roth 401(k) there is no withholding reduction, so $100 contributed cuts your take-home by the full $100. Run the numbers alongside the take-home paycheck calculator to see the full net-pay picture.
Does a 401(k) contribution reduce Social Security and Medicare taxes?
No, and this is the most common mistake in 401(k) math. Elective deferrals are excluded from your federal income tax wages (W-2 Box 1) but are still fully included in Social Security and Medicare wages (Boxes 3 and 5). You pay the full 6.2% and 1.45% on your gross whether you defer or not. That is why the gap between Box 1 and Box 3 on your W-2 is usually your 401(k). HSA, FSA, and Section 125 health premiums are different: those do reduce FICA wages.
What is the difference between a Traditional and a Roth 401(k) on my paycheck?
Traditional comes out before income tax, so your paycheck drops by less than you contribute and you pay tax on withdrawals later. Roth comes out after income tax, so your paycheck drops by the exact contribution amount and qualified withdrawals are tax-free. Neither one changes your FICA. Both are eligible for the employer match. Switch the contribution type chip above to see the two side by side at your own pay rate.
Does the employer match show up in my paycheck?
No. The match goes straight into your 401(k) account. It never passes through your net pay and it is not withheld from your wages, which is why this calculator keeps it in its own block and out of every take-home figure. The match also does not count against your annual elective deferral limit, which caps only what you put in. A separate, much higher Section 415(c) annual additions limit covers your money and your employer's money combined.
What percentage do I need to contribute to max out my 401(k) in 2026?
Divide the 2026 elective deferral limit by your annual gross pay. If you earn $80,000, the $24,500 limit works out to about 30.6% of pay, or roughly $942 per paycheck if you are paid biweekly. If you are 50 or older you can defer an extra $8,000, and if you are 60 to 63 the catch-up is $11,250 instead. Not sure what your annual gross is? The salary vs hourly calculator converts a rate and a schedule into an annual figure.
What if I hit the 401(k) limit before the end of the year?
Your payroll system stops your deferrals for the rest of the year. That is fine for the tax break, but if your employer matches per paycheck rather than annually, you miss match on every paycheck after your deferrals stop, unless the plan offers a year-end true-up. Ask HR about the true-up before you front-load contributions. The pay period converter helps when your plan states limits per month and you are paid biweekly.
My employer matches 50% up to 6%. What should I contribute?
At least 6%. Anything under that leaves free money behind: at 3% you get half the match you could have had. Contributing above 6% does not earn any more match, but the extra dollars still get the pre-tax break if you are using a Traditional 401(k). This calculator shows the exact dollar amount you are leaving on the table at your current rate, plus the rate you would need to capture all of it.
Do I have to make catch-up contributions as Roth now?
Starting in 2026, if you earned more than $150,000 from your employer in the prior year, catch-up contributions to an employer plan must be made on a Roth (after-tax) basis. Those catch-up dollars will not reduce your current paycheck's income tax at all, so model them with the Roth chip before you set your rate. Everything below the catch-up amount can still go in pre-tax.