How this calculator works
Contribution × entered marginal income-tax rates. Traditional 401(k) contributions generally do not reduce Social Security or Medicare wages.
When this result is useful
This tool estimates how a traditional 401(k) contribution can reduce current federal and modeled state income-taxable wages. It is useful for seeing why a $100 contribution generally reduces take-home by less than $100, while still moving the full contribution into the retirement account.
How to interpret the output
The estimated tax saving uses the marginal income-tax rates entered by the user. Traditional 401(k) deferrals generally remain subject to Social Security and Medicare, so the calculator does not apply the marginal rate to FICA. Roth contributions have different current-tax treatment and should not be modeled as traditional contributions here.
Worked example
A 6% contribution on $75,000 is $4,500. At a combined 27% marginal income-tax rate, estimated tax savings are $1,215.
Common mistakes to avoid
- Entering an effective tax rate instead of a marginal rate.
- Assuming every state follows the same treatment as federal law.
- Ignoring plan limits, employer matching rules, vesting, or payroll timing.
Assumptions and limits
Inputs are treated as non-negative U.S. dollar amounts. Results are rounded to cents where useful. This tool is for planning and does not determine legal eligibility, payroll compliance, or final tax liability.
Check the plan document and payroll election screen, then use the main calculator's annual traditional 401(k) field to see the contribution alongside other deductions and taxes.
Official reference
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