How a 401k Contribution Affects Your Paycheck and Taxes
- Projected balance (at retirement)
- 1.846.072 $
- Investment growth
- 1.366.123 $
A traditional 401k contribution lowers your take-home pay by less than the amount you save, because it comes out before income tax. If you contribute $200 and your combined marginal tax rate is 25%, your take-home drops by only about $150 — the other $50 is income tax you deferred. A Roth contribution is after-tax, so take-home falls by the full $200 instead. The higher your bracket, the larger this cushion, which is one reason 'saving your raise' barely dents your take-home pay. One important boundary: a traditional contribution reduces income tax but not Social Security and Medicare (FICA) tax, which is 7.65% of gross wages for most employees and still applies to your full pay — so your paycheck does not drop by quite as little as the income-tax math alone would suggest.
Published · Last verified · Written and fact-checked by Ali Raza · Our methodology · Terms explained
Why does saving $200 cost your paycheck less than $200?
A traditional 401k contribution is deducted from your pay before income tax is calculated. That means it lowers your taxable income, so part of what you 'save' is money you would otherwise have paid in tax anyway. Your take-home pay drops by less than the full contribution.
For example, if you contribute $200 from a paycheck and your combined marginal tax rate is 25%, your take-home pay falls by only about $150. The other $50 is income tax you deferred. In effect, the government is subsidizing part of your retirement contribution.
How do traditional and Roth affect your paycheck differently?
The paycheck impact depends on which type of contribution you make. A traditional contribution reduces your taxable income now, so the take-home hit is cushioned by the tax break. A Roth contribution is made with after-tax dollars, so your take-home pay drops by the full contribution amount.
Neither is automatically better — it is the same Roth-vs-traditional decision viewed through your paycheck. The Roth costs more today in exchange for tax-free withdrawals later; the traditional costs less today but is taxed in retirement.
| Contribution type | You save | Tax deferred | Take-home drop |
|---|---|---|---|
| Traditional | $200 | $50 | $150 |
| Roth | $200 | $0 | $200 |
Does a 401k contribution reduce FICA taxes?
There is an important exception to the tax break. A traditional 401k contribution lowers the income subject to federal and state income tax, but it does not reduce the wages subject to Social Security and Medicare taxes (FICA). Those are still withheld on your full gross pay.
This is why your paycheck does not drop by quite as little as the income-tax math alone suggests. FICA is 7.65% of gross wages for most employees and applies regardless of how much you contribute to a traditional 401k. Our 401k FAQ hub answers more questions about 401k and take-home pay.
Why does a higher tax bracket help more?
The size of the take-home cushion depends on your marginal tax rate. Someone in a 12% bracket sees a smaller cushion than someone in a 32% bracket, because the higher earner defers more tax per dollar contributed. This is one reason traditional contributions are often attractive to high earners.
It also explains why the popular advice to 'save your raise' works so well. Because the take-home impact of a contribution is smaller than the contribution itself, directing part of a pay rise into your 401k barely changes your take-home pay while meaningfully increasing your savings.
- Traditional contributions cut take-home by less than the amount saved.
- Roth contributions cut take-home by the full amount.
- FICA taxes still apply to your gross pay regardless of contribution type.
- A higher tax bracket means a larger take-home cushion on traditional contributions.
How does the employer match improve the deal?
None of this counts the employer match, which adds money to your account without affecting your paycheck at all. When you factor in that a modest take-home reduction can be matched dollar-for-dollar or fifty cents on the dollar, the effective return on a 401k contribution is hard to beat.
A 401k paycheck calculator lets you enter your gross pay, contribution rate, and tax rate to see the real take-home impact before you change anything — usually revealing that saving more costs less than people expect.
Frequently asked
A traditional contribution reduces take-home pay by less than the amount you save, because it lowers your taxable income. At a 25% marginal rate, a $200 contribution cuts take-home by about $150. A Roth contribution cuts it by the full $200.