401(k) Contribution Tax Savings Calculator
See how much a traditional 401(k) contribution really costs after the tax savings.
This is an estimate for the 2026 tax year, not tax, legal, or financial advice. Figures are simplified and don't include every credit or deduction. Talk to a tax professional before making decisions.
How this is calculated
A traditional 401(k) contribution comes out of your paycheck before federal and state income tax are calculated. That means every dollar you contribute shrinks your taxable income by a dollar, which lowers your tax bill — but it doesn't lower it dollar-for-dollar, because you only save your marginal tax rate on that money, not the full amount.
We calculate your taxes twice with the same salary, filing status, and state: once with your chosen contribution and once with a $0 contribution. The difference in federal and state tax between those two runs is your total tax saved.
Subtracting the tax you saved from the amount you contributed gives the real cost to your take-home pay — usually noticeably less than the contribution itself, since part of it is money you would have paid in tax anyway.
The 2026 employee 401(k) contribution limit is shown below the contribution field. It doesn't include any employer match, and this calculator doesn't account for catch-up contributions if you're 50 or older.