How do traditional 401(k) contributions change take-home pay?
By Kyu-Hun Lee · Published
Short answer: A traditional pre-tax 401(k) deferral generally reduces current federal income-taxable wages, but employee Social Security and Medicare wages still include the deferral. The contribution also moves money out of current spendable pay and into retirement savings. A Roth deferral has different current income-tax treatment.
Tax savings do not equal the contribution
Suppose you defer an additional $10,000 and, solely for illustration, all of it would otherwise face a 24% federal marginal rate. The simple federal income-tax reduction is $2,400, leaving a $7,600 reduction in current cash before state effects and other interactions. The full $10,000 goes toward retirement savings; it has not disappeared from your compensation.
That illustration is not a contribution-limit statement or an individualized estimate. Crossing brackets, your state’s treatment, eligibility rules and other tax items can change the result. Use the plan’s current limits and your actual payroll elections when building a budget.
Sources: IRS 401(k) resource guide: plan participant overview
Compare the employer match separately from salary
Write down the match formula, the contribution needed to receive it, and the vesting schedule. A contribution subject to future service requirements should not be treated as immediately available cash. A valuable retirement benefit can make an offer more attractive without paying this month’s rent.
Check other benefits alongside the match: employee insurance premiums, out-of-pocket exposure, paid leave and any commuting costs. A single total-compensation number hides when and how each benefit becomes usable. Compare recurring spendable cash and longer-term benefits in separate columns.
How to use the current TrueTaxCalc model
The current tax and offer calculators do not model pre-tax retirement deferrals. Do not simply subtract a traditional 401(k) contribution from the salary input: that can incorrectly reduce the modeled Social Security and Medicare tax base. Use full wage compensation and treat the displayed take-home figure as before retirement deductions.
For a retirement-adjusted estimate, reconcile with a payroll calculator that accepts separate deduction types or your employer’s payroll projection. You can enter an after-tax cash expense in the offer budget for budgeting purposes, but doing that does not calculate the tax benefit of a pre-tax deferral.
Sources: IRS 401(k) resource guide: plan participant overview
Put your own offer into the comparison
Separate recurring salary, bonus and sellable RSUs from a signing payment and moving costs. Change the assumptions and download a free report.
Compare my offersCommon questions
Does a traditional 401(k) contribution reduce FICA wages?
Generally no. Elective deferrals are still included in Social Security and Medicare wages even when excluded from current federal income-taxable wages.
Does this tool calculate Roth versus traditional contributions?
No. The current model excludes retirement contributions and should not be used to choose between those tax treatments.
Sources and scope
Source links checked September 24, 2026. Check the year displayed on tax forms; some sources explain general rules using prior-year examples. These guides are educational and have not been independently reviewed by a tax professional. Our calculator supports a narrower set of scenarios than the rules discussed here. Read the model’s scope.