Roth vs. Traditional 401(k): The Tax Bracket Bet
Choosing between Roth and Traditional 401(k) contributions is a bet on your future tax bracket. Pay taxes now or later? The right answer depends on income trajectory and retirement goals.
Compare net outcomes
Model both options with our tax shield analysis.
Roth 401(k): pay taxes now
Roth contributions are after-tax, but withdrawals are tax-free later. This can be powerful if you expect a higher tax bracket in retirement.
Your paycheck shrinks by the full contribution plus the income tax you still owe on that money. In exchange, a qualified distribution โ generally one taken after age 59ยฝ and at least five years after your first Roth contribution to the plan โ comes out free of federal income tax, including all the growth. Since 2024, designated Roth accounts in 401(k) plans are no longer subject to required minimum distributions during the owner's lifetime, which removes one of the old drawbacks compared with a Roth IRA.
Traditional 401(k): defer taxes
Traditional contributions reduce taxable income now, but withdrawals are taxed later. This usually wins when your retirement tax rate is lower.
Pre-tax deferrals come out of your paycheck before federal income tax (and usually state income tax), so a $1,000 contribution costs someone in the 22% bracket only about $780 of take-home pay. Note that Social Security and Medicare (FICA) taxes still apply to 401(k) deferrals of either type. Every dollar you later withdraw โ contributions and growth โ is taxed as ordinary income, and required minimum distributions generally begin at age 73.
Side-by-side comparison (2026)
| Feature | Traditional 401(k) | Roth 401(k) |
|---|---|---|
| Tax on contributions | Deferred (lowers taxable income now) | Taxed now |
| Tax on qualified withdrawals | Ordinary income | Tax-free |
| 2026 employee limit | $24,500 combined across both types; +$8,000 catch-up at 50+; $11,250 instead for ages 60โ63 | |
| Income limit to contribute | None | None (unlike a Roth IRA) |
| Lifetime RMDs | Yes, generally from age 73 | No (since 2024) |
| Employer match | Pre-tax | Usually pre-tax; Roth match only if the plan allows |
The $24,500 limit is one bucket: you can split it any way you like between Roth and Traditional, but not contribute $24,500 to each. Under SECURE 2.0, higher earners (based on prior-year FICA wages above an inflation-indexed threshold) must make their catch-up contributions as Roth starting in 2026, so check how your plan handles this.
The math: why equal tax rates tie
The cleanest way to compare the two is to hold your take-home cost constant. A $10,000 Traditional contribution in the 22% bracket costs the same $7,800 of take-home pay as a $7,800 Roth contribution.
- โข Roth: $7,800 grows to about $59,376 โ all tax-free
- โข Traditional: $10,000 grows to about $76,123 before tax
- โข Withdrawn at 22%: $59,376 after tax โ an exact tie
- โข Withdrawn at 12%: $66,988 after tax โ Traditional wins by ~$7,600
- โข Withdrawn at 24%: $57,853 after tax โ Roth wins by ~$1,500
The takeaway: the account type doesn't change your investment return. Only the difference between today's tax rate and the rate on your future withdrawals decides the winner. (The Roth has one quiet edge: if you max out the limit, a Roth dollar holds more after-tax value than a Traditional dollar, so Roth effectively lets you shelter more.)
Marginal in, effective out
Traditional deferrals save tax at your marginal rate โ the rate on your top dollars. In retirement, withdrawals fill the brackets from the bottom, starting with the standard deduction.
- โข Minus the $32,200 standard deduction = $27,800 taxable
- โข First $24,800 at 10% = $2,480; next $3,000 at 12% = $360
- โข Total federal tax: $2,840 โ about 4.7% of the withdrawal
If that couple deferred the money while in the 22% or 24% bracket, Traditional was the better bet. Real retirees often have Social Security, pensions, or taxable investment income stacked on top, which pushes withdrawals into higher brackets โ so plug your own numbers in rather than assuming.
How to make the bet
If you're early in your career or expect higher income later, Roth often makes sense. If you're in a high tax bracket now, Traditional can deliver bigger savings.
Find your marginal bracket today
Example: a single filer earning $85,000 has $68,900 of taxable income after the $16,100 standard deduction โ inside the 22% bracket ($50,400โ$105,700). A $10,000 Traditional deferral saves about $2,200 of federal tax.
Watch bracket edges
Example: a married couple earning $250,000 has $217,800 taxable โ $6,400 into the 24% bracket. Deferring $24,500 saves $6,400 ร 24% + $18,100 ร 22% = $5,518. Pre-tax savings beyond the bracket edge are worth a little less.
Estimate retirement income honestly
Add expected Social Security, pensions, RMDs from a large pre-tax balance, and any planned move to a higher- or lower-tax state. A big Traditional balance can force large RMDs later.
When unsure, split
Nobody knows future tax law. Splitting contributions builds "tax diversification" โ pre-tax and Roth buckets you can draw from strategically each year in retirement.
Other factors that can tip the scale: a lower adjusted gross income from Traditional deferrals can help you qualify for income-tested benefits such as the Child Tax Credit or ACA premium tax credits, and keep you under the phase-outs for a Roth IRA. To see how a bigger deferral changes your paycheck, read what maxing out your 401(k) does to take-home pay.
Common mistakes
- โข Comparing equal contributions instead of equal take-home cost. $10,000 Roth costs more than $10,000 Traditional; compare like for like.
- โข Using your effective rate today. The relevant saving today is your marginal rate.
- โข Assuming retirement income will be tiny. Large pre-tax balances, pensions, and Social Security can keep you in the same bracket.
- โข Skipping the match to chase Roth. Contribute enough to get the full employer match whichever type you pick.
- โข Forgetting state taxes. Moving from a high-tax state to a no-income-tax state in retirement favors Traditional, and vice versa.
Frequently Asked Questions
Can I contribute to both a Roth and a Traditional 401(k)?
Yes, if your plan offers both. Your combined employee deferrals can't exceed $24,500 in 2026 (plus any catch-up you qualify for).
Is there an income limit for the Roth 401(k)?
No. Unlike a Roth IRA, which phases out at $153,000โ$168,000 of MAGI for single filers in 2026, the Roth 401(k) is available at any income level if your plan offers it.
Does a Roth 401(k) save FICA taxes?
No โ neither type does. Social Security and Medicare taxes apply to 401(k) deferrals either way. Only certain payroll deductions, such as HSA contributions through a cafeteria plan, avoid FICA.
What if I'm in the 12% bracket?
Roth is often attractive at 12% because the tax cost now is low and many people's retirement rate ends up similar or higher. It still depends on your expected retirement income.
Sources
- โข IRS Notice 2025-67 (2026 retirement plan limits) โ IRS Retirement Plans
- โข IRS Rev. Proc. 2025-32 (2026 tax brackets and standard deduction) โ irs.gov
- โข IRS Publication 575, Pension and Annuity Income
This article is educational and is not individualized tax or investment advice. Examples are hypothetical.
Anand Godar
Financial engineer and founder of QuantCurb. Former fintech data scientist building source-cited financial calculators for everyday wealth decisions.
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