US 401(k) tax savings calculator
How much federal and state income tax a traditional 401(k) contribution saves you in 2026, and what it really costs your pay.
An estimate only. It assumes a traditional (pre-tax) contribution within the annual limit, which the IRS sets each year and which you should check. Social Security and Medicare tax are not reduced by a 401(k). Withdrawals in retirement are taxed. Check the IRS for current limits.
How this calculator works
A traditional 401(k) contribution is deducted from your income before federal income tax is worked out, so the saving is the difference between the tax with and without it. The saving is roughly your top federal rate times the contribution, plus any state tax saved.
Worked example: a single filer on $85,000 pays $9,870 of federal tax. A $10,000 contribution lowers taxable income to $58,900 and the tax to $7,670, a saving of $2,200, which is 22%. The contribution really costs $7,800 of take-home pay.
Sources and checks
Our figures and rules follow these official sources:
- IRS: Tax inflation adjustments for tax year 2026
- IRS: Topic no. 751, Social Security and Medicare withholding rates
Check the IRS for the current annual contribution limit, which this calculator does not apply.
Figures last checked: 30 October 2026. Spotted a mistake? Tell us.