401(k) Contribution Impact Calculator
See how a 401(k) contribution really affects your take-home pay.
Formula
About this calculator
The single biggest reason people under-contribute to their 401(k) is a misunderstanding: they assume a $6,000 contribution costs them $6,000 in spending money. It doesn't. Because a traditional 401(k) is funded with pre-tax dollars, every dollar you contribute lowers your taxable income — so your take-home pay falls by noticeably less than the amount you actually save.
This calculator shows both numbers at once. Enter your salary, contribution percentage, employer match and state, and it computes how much smaller your paycheck gets versus how much money lands in your 401(k). The gap between the two is your income-tax saving. A contribution reduces federal and state income tax, but note that Social Security and Medicare are still charged on your full salary, so those don't shrink.
Then there's the part that is simply free money: the employer match. If your company matches 100% up to 3% of salary and you contribute at least that much, you instantly double those dollars. Skipping the match is leaving guaranteed, tax-advantaged return on the table. Adjust the inputs to find the contribution level that captures the full match while keeping your paycheck comfortable.
Frequently asked questions
How much does a 401(k) contribution reduce my paycheck?
By less than the contribution itself, because traditional 401(k) money is pre-tax. If you're in a 22% federal bracket plus state tax, a $100 contribution might reduce your take-home by only about $70 — the rest is income tax you would have paid anyway.
Does a 401(k) reduce Social Security and Medicare tax?
No. Traditional 401(k) contributions lower your federal and state income tax, but FICA taxes (6.2% Social Security and 1.45% Medicare) are still charged on your full gross salary.
Should I always contribute enough to get the full match?
In almost all cases, yes. An employer match is an immediate, guaranteed return on your money — often a 50%–100% instant gain — so capturing the full match is usually the first priority before other investing.
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⚠️ This is a simplified estimate for a single filer and is for planning only — not tax advice. Contribution limits, filing status and plan rules vary. Confirm details with your plan administrator or a financial professional.