Skip to content
Investigator Finance

Calculator

Roth vs. traditional 401(k) calculator

Many workplace plans let you choose: a Roth 401(k), where you pay tax now and qualified withdrawals are tax-free, or a pre-tax (traditional) 401(k), where you skip tax now and pay it when you withdraw. Enter what you contribute, your age and your tax bracket now and later for an after-tax comparison. Deciding between IRAs instead? Use the Roth vs. traditional IRA calculator.

Educational only, not financial advice

This tool shows general math, not a recommendation for you. It isn’t financial, tax or legal advice, and real returns, fees and tax rules will differ. Talk to a qualified professional before making decisions. What you enter stays in your browser: nothing is saved or sent to us.

$

Your 2026 limit: $24,500, Roth and pre-tax combined. Employer match is separate.

2026 brackets, by taxable income (after deductions).

In today’s brackets.

%

Default: 5%. An assumption, not a forecast. Same for both.

Based on these assumptions

Roth 401(k) likely comes out ahead by about $137,023

After tax, in today’s dollars, valued at retirement (age 65).

Roth 401(k) $664,388, pre-tax 401(k) $527,365.

Break-even: Pre-tax wins only if your combined tax rate in retirement is below about 7.2%. You entered 22%.

If you invested the pre-tax savings instead: Roth 401(k) ahead by about $71,144.

What drives this

  • Both get $10,000 a year. The Roth balance ($664,388) is all yours; the pre-tax balance ($664,388) still owes income tax. Because Roth dollars are after tax, the same $24,500 limit shelters more money in a Roth.
  • Pre-tax lowers your tax bill now by about $2,200 a year. That's counted as spent ($66,000 in total, no growth).
  • Pre-tax withdrawals can make more of your Social Security taxable and add Medicare IRMAA surcharges, about $56,858. Qualified Roth withdrawals don’t count toward either.
Advanced options(state tax, tax savings, RMDs and more)

Changes the bracket ranges and the Social Security and Medicare checks.

Default: 25. The account is spent down evenly.

%

Assumes pre-tax contributions lower your state tax too. Check your state’s rule.

%

Blank: same as now. Use 0 if you plan to move to a state without income tax.

The pre-tax tax savings

Pre-tax lowers your taxes today. Invested savings go in a taxable account, where dividends and gains are taxed.

On: you defer the same $10,000 either way (Roth costs more take-home). Off: Roth gets the amount minus today’s tax, so both cost the same.

Pre-tax 401(k)s generally must pay out from 73 (75 if born in 1960 or later). Roth 401(k)s have had no lifetime RMDs since 2024. Still working past that age? Many plans let you wait until you retire.

Employer match

Your employer’s match usually goes in pre-tax no matter which option you pick, so it’s the same either way and doesn’t change this comparison. Under SECURE 2.0, a plan may let you take matches as Roth instead, which are then taxed to you as income now. Check your 401(k) match.

Why the Roth 401(k) often comes out ahead

If your tax rate in retirement will be clearly lower than today, pre-tax can still win, and the calculator will say so. But several things tilt toward Roth that a simple “rate now vs. rate later” guess misses:

  • More money sheltered at the limit. The $24,500 limit is the same for both, but Roth dollars are after tax. Contributing $24,500 to a Roth 401(k) protects more future growth than $24,500 pre-tax.
  • Tax-free growth. Qualified Roth withdrawals, earnings included, aren’t taxed.
  • No RMDs. Since 2024, designated Roth 401(k) accounts don’t have required minimum distributions while you’re alive. Pre-tax balances must start paying out at 73 or 75, whether you need the money or not.
  • Lower taxable income in retirement. Roth withdrawals don’t make more of your Social Security taxable or push you into Medicare’s IRMAA surcharges.
  • Tax diversification. Nobody knows future tax rates. Having both Roth and pre-tax money lets you choose which to draw from each year. That flexibility isn’t in the number above.

Pre-tax helps most when your bracket today is high and you expect a much lower one in retirement, or when you’d invest the tax savings every year. Splitting contributions between the two is also allowed.

How it compares

  • Same engine as our IRA calculator. Everything is in today’s dollars. The Roth result is the balance at retirement; the pre-tax result is every after-tax withdrawal, valued at retirement, plus the tax savings from contributing. See the Roth vs. traditional IRA calculator for every assumption.
  • 2026 limits. You can defer up to $24,500, Roth and pre-tax combined, plus a $8,000 catch-up at 50 or older ($11,250 at 60 to 63). If your prior-year wages from the employer were over $150,000, catch-ups must be Roth.
  • Employer match. It usually goes in pre-tax either way, so it doesn’t change the comparison. A plan may now let you take it as Roth, taxed to you now. See the 401(k) match calculator.
  • Not modeled: the still-working RMD delay, early withdrawals and the 5-year rule for qualified Roth withdrawals, rolling a Roth 401(k) into a Roth IRA, heirs, and future tax law changes.

Results are estimates based on these assumptions, for education only, not tax advice.

Sources

Checked .