How this 401(k) paycheck calculator works
The calculator runs the same 2026 paycheck calculation as the take-home pay calculator twice: once with no 401(k) and once with your contribution. The difference between the two paychecks is what your 401(k) really costs you in take-home pay.
- Contribution. A percentage of pay or a dollar amount per paycheck, limited to the 2026 IRS limit for your age group and to the pay you have left after other pre-tax deductions.
- Traditional 401(k). The contribution is subtracted before federal income tax withholding is figured with the IRS Publication 15-T percentage method, and before a flat state rate if you enter one.
- Roth 401(k). The contribution is taken from pay after income tax, so federal and state withholding do not change.
- Social Security and Medicare. These are figured on your pay before the 401(k) in both cases, so they do not change.
Take-home pay = gross pay - 401(k) - federal tax - Social Security - Medicare - state tax - other deductions
Worked examples
What the results mean
Take-home pay you give up is the difference between the paycheck without a 401(k) and with it. For a traditional 401(k) it is smaller than the contribution, and the gap is the income tax you save. Income tax saved per year is that per-paycheck saving times your number of paychecks. It is a saving in withholding now, not a tax-free gain, because traditional 401(k) withdrawals are taxed later.
Employer match is shown separately because it is paid by your employer and does not reduce your take-home pay.
2026 numbers used
| Item | 2026 figure |
|---|---|
| 401(k) employee limit | $24,500 |
| Catch-up, age 50 and older | $8,000 (total $32,500) |
| Catch-up, ages 60 to 63 | $11,250 (total $35,750) |
| Social Security tax (employee) | 6.2% on wages up to $184,500 |
| Medicare tax (employee) | 1.45% on all wages |
| Standard deduction behind the withholding tables | $16,100 single, $32,200 married filing jointly, $24,150 head of household |
Assumptions and limits
- Federal withholding uses the standard percentage method for a Form W-4 filed in 2020 or later. The Step 2 multiple jobs box is not modeled.
- State tax is either zero or a flat rate you choose, applied as if the state exempts a traditional contribution. A few states tax 401(k) contributions, and real state withholding uses each state's own tables.
- The results show a regular paycheck early in the year. Withholding is not the same as your final tax, which is settled on your tax return.
- Rules that require some higher earners to make catch-up contributions as Roth, employer profit sharing and the overall plan limit on employer and employee contributions are not modeled.
- Local taxes, state payroll programs and employer-specific rules are not included.
- This works for salaried pay. For an hourly wage, convert it with the hourly to salary calculator first.
Sources
Rules reviewed October 2026 against: IRS 2026 retirement plan limits; IRS Publication 15-T (2026), Federal Income Tax Withholding Methods; IRS Publication 15 (2026), Employer’s Tax Guide; Social Security Administration, contribution and benefit base. Tax law and limits change, so confirm current figures with the IRS or a tax professional.
Frequently asked questions
Does a 401(k) contribution lower my paycheck by the full amount?
Not with a traditional 401(k). The contribution comes out of your pay before federal income tax, so your income tax withholding falls and your take-home pay drops by less than you contribute. A Roth 401(k) is taken from after-tax pay, so your take-home pay drops by the full contribution.
Does a 401(k) reduce Social Security and Medicare tax?
No. 401(k) contributions still count as wages for Social Security and Medicare, so those taxes are the same with or without a contribution. Only federal income tax, and state income tax in most states, is reduced by a traditional 401(k).
What is the 2026 401(k) contribution limit?
The employee limit is $24,500 for 2026. People 50 and older can add a $8,000 catch-up for $32,500, and ages 60 to 63 can add $11,250 for $35,750. An employer match does not count toward your own limit.
Should I choose a traditional or a Roth 401(k)?
A traditional 401(k) gives a larger paycheck now because the contribution is untaxed today and taxed when you withdraw it. A Roth 401(k) gives a smaller paycheck now and, if the rules are met, tax-free withdrawals later. The comparison table on this page shows the paycheck difference. The right choice depends on your tax situation, so consider a tax professional.
How much of my pay should I contribute?
There is no single right percentage. A common starting point is enough to receive your employer's full match, since the match is extra pay for saving. Use this calculator to see what each percentage costs in take-home pay before you choose.