How Maxing Your 401(k) Affects Your Paycheck More Than You Think

The 2025 contribution limit for a 401(k) is $23,500. A lot of people look at that number, divide it across their paychecks, and assume their take-home pay will drop by the full amount. It won't — and understanding why is the key to deciding how much you can actually afford to contribute.

Traditional 401(k) contributions are pre-tax

When you contribute to a traditional 401(k), the money comes out of your paycheck before income tax is calculated. That means every dollar you contribute also reduces your taxable income by a dollar. So while your gross pay drops by the full contribution, your take-home only drops by the contribution minus the tax you would have paid on that money.

The real math

Say you're in the 22% federal bracket and live in a state with a 5% income tax. For every $100 you contribute to your traditional 401(k):

• Your gross pay drops by $100
• But you save $22 in federal tax and $5 in state tax
• So your actual take-home only drops by about $73

Contributing the full $23,500 in that scenario reduces your take-home pay by roughly $17,000, not $23,500. The other $6,500 or so is money that would have gone to taxes anyway — now it's sitting in your retirement account instead.

Note: FICA still applies

One important detail — 401(k) contributions reduce your income and state tax, but they do not reduce Social Security and Medicare (FICA) taxes. Those 7.65% payroll taxes are calculated on your full salary before the 401(k) deduction. So the "discount" applies to income tax only, not payroll tax.

Traditional vs. Roth

Everything above applies to traditional 401(k) contributions. A Roth 401(k) works the opposite way: you contribute after-tax dollars, so your take-home drops by the full amount now, but qualified withdrawals in retirement are tax-free. If you expect to be in a higher tax bracket later, Roth can be the better long-term choice even though it stings more today.

Don't leave the match on the table

Whatever you decide about maxing out, contribute at least enough to capture your full employer match. A typical match of 50% on the first 6% of salary is an instant, guaranteed 50% return on that money — the best deal in personal finance, and it disappears if you don't contribute enough to earn it.