What is the difference between a traditional 401k and a Roth 401k?

A traditional 401k reduces your taxable income now (pre-tax contributions) but withdrawals in retirement are taxed as ordinary income. A Roth 401k uses after-tax money, so withdrawals in retirement are completely tax-free — including all the growth.

Which is better: traditional 401k or Roth?

If you expect to be in a higher tax bracket in retirement than today, Roth wins. If you expect a lower bracket in retirement, traditional wins. The calculator shows the after-tax outcome for your specific current and projected tax rates.

Can I contribute to both a traditional and Roth 401k?

Yes. If your employer offers both, you can split your contributions between them up to the annual 401k limit ($23,500 in 2025, plus $7,500 catch-up if age 50+). This gives you tax diversification in retirement.

What about employer matching?

Employer matches on Roth contributions are typically deposited into a traditional (pre-tax) account, regardless of which type you contribute to. So even a pure Roth strategy still produces some pre-tax dollars from the match.

Are there income limits for contributing to a Roth 401k?

No — unlike a Roth IRA, a Roth 401k has no income limits. Anyone whose employer offers a Roth 401k option can contribute, regardless of income. Roth IRA contributions, however, phase out at $146,000 (single) and $230,000 (married filing jointly) in 2024.

What are required minimum distributions (RMDs) and how do they differ?

Traditional 401k accounts require you to begin taking minimum withdrawals at age 73. These RMDs are taxed as ordinary income and can push you into a higher bracket. Roth 401k accounts were previously subject to RMDs, but the SECURE 2.0 Act (effective 2024) eliminated RMDs for Roth 401k accounts — a major advantage for leaving money to grow or for estate planning.

401k vs Roth Calculator

Compare the long-run after-tax value of a traditional 401(k) versus a Roth IRA. See exactly when a Roth pays off more — and when it does not — based on your current and expected retirement tax rates.

Traditional wins by

When current and retirement tax rates are equal, both accounts tie on an after-tax basis.

Traditional after-tax

$515,756

Roth (tax-free)

$515,756

Trad. pre-tax balance

$661,226

Roth (after-tax, tax-free at withdrawal)Traditional (after-tax, applying retirement rate)

Traditional vs. Roth: the tax rate gamble

The core difference between a Traditional 401(k) and a Roth 401(k) comes down to when you pay taxes. Traditional contributions reduce your taxable income now but are taxed as ordinary income when withdrawn in retirement. Roth contributions use after-tax dollars now and are completely tax-free in retirement — including all the growth.

The right choice depends on one question: will your marginal tax rate be higher in retirement or lower than it is today? If you're in your prime earning years with a high tax bracket now and expect a lower income in retirement, Traditional wins. If you expect taxes to rise (or your retirement income will include large Roth balances or conversions), Roth wins. This calculator shows the after-tax outcome for your specific rate assumptions.

Why it matters to your money

Over a working career, the difference between Traditional and Roth can amount to tens of thousands of dollars in after-tax retirement income. The decision becomes even more nuanced with employer matching (which typically goes into Traditional accounts regardless), part-time Roth conversions, and the possibility of future tax rate changes. Tax diversification — having both pre-tax and post-tax retirement savings — is generally considered a prudent strategy regardless of which is "better."

Read the full explainer on 401(k) vs. Roth IRA for a detailed comparison of all the account types, tax implications, and strategies for combining them over your working career.

Rules of thumb

Current bracket > expected retirement bracket → Traditional: If you're in the 24%+ bracket now and expect Social Security + pension to put you in the 12–22% bracket in retirement, the Traditional deduction is worth more.
Current bracket < expected retirement bracket → Roth: If you're early career with a lower tax bracket now (or expect large Roth conversions or business income in retirement), lock in today's lower rates.
Tax diversification is smart: Contribute to both a Traditional and Roth account up to the annual limit. Having both pre-tax and post-tax retirement money gives you flexibility in retirement to manage your taxable income.

Traditional 401k vs. Roth 401k: feature comparison

Beyond the tax-timing question, the two account types differ in several structural ways that matter for planning — especially around withdrawals, required distributions, and income limits. The table below summarizes the key differences using 2025 figures.

Feature	Traditional 401k	Roth 401k
Contributions taxed	Pre-tax (reduces taxable income now)	After-tax (no deduction today)
Withdrawals in retirement	Taxed as ordinary income	Tax-free (incl. growth)
2025 contribution limit	$23,500 ($31,000 age 50+)	$23,500 ($31,000 age 50+)
Income limits to contribute	None	None
Required minimum distributions	Yes, starting at age 73	No (eliminated by SECURE 2.0)
Early withdrawal (before 59½)	10% penalty + income tax	10% penalty on earnings only; contributions accessible after 5 years
Best when	Current tax rate > expected retirement rate	Current tax rate < expected retirement rate

One often-overlooked advantage of the Roth 401k: the elimination of required minimum distributions under SECURE 2.0 means you can leave the account untouched indefinitely, letting it continue compounding tax-free. This makes the Roth 401k particularly powerful for estate planning or for retirees who don't need the funds immediately.

Frequently asked questions

What is the difference between a traditional 401k and a Roth 401k?: A traditional 401k reduces your taxable income now (pre-tax contributions) but withdrawals in retirement are taxed as ordinary income. A Roth 401k uses after-tax money, so withdrawals in retirement are completely tax-free — including all the growth.
Which is better: traditional 401k or Roth?: If you expect to be in a higher tax bracket in retirement than today, Roth wins. If you expect a lower bracket in retirement, traditional wins. The calculator shows the after-tax outcome for your specific current and projected tax rates.
Can I contribute to both a traditional and Roth 401k?: Yes. If your employer offers both, you can split your contributions between them up to the annual 401k limit ($23,500 in 2025, plus $7,500 catch-up if age 50+). This gives you tax diversification in retirement.
What about employer matching?: Employer matches on Roth contributions are typically deposited into a traditional (pre-tax) account, regardless of which type you contribute to. So even a pure Roth strategy still produces some pre-tax dollars from the match.
Are there income limits for contributing to a Roth 401k?: No — unlike a Roth IRA, a Roth 401k has no income limits. Anyone whose employer offers a Roth 401k option can contribute, regardless of income. Roth IRA contributions, however, phase out at $146,000 (single) and $230,000 (married filing jointly) in 2024.
What are required minimum distributions (RMDs) and how do they differ?: Traditional 401k accounts require you to begin taking minimum withdrawals at age 73. These RMDs are taxed as ordinary income and can push you into a higher bracket. Roth 401k accounts were previously subject to RMDs, but the SECURE 2.0 Act (effective 2024) eliminated RMDs for Roth 401k accounts — a major advantage for leaving money to grow or for estate planning.

Learn more

401k vs Roth IRA: which one actually wins? — The Traditional vs Roth decision is entirely about tax rates — when you pay them, and whether they go up or down. Here's the math, the intuition, and how to decide which account is right for your situation.
The backdoor Roth IRA, step by step — High earners can't contribute to a Roth IRA directly — but they can contribute to a traditional IRA and convert it. Here's exactly how the backdoor Roth works, the pro-rata trap that blows it up, and when to bother.
The Complete Guide to Retirement Planning — How to build a retirement plan from scratch: how much to save, which accounts to use, how to invest, and how to figure out when you can retire.
Tax-loss harvesting basics — Tax-loss harvesting turns portfolio losses into a tax deduction — without meaningfully changing your investment position. Here's how it works, what it's worth, and the wash-sale rule you must not violate.