Compare Roth and traditional after-tax value.
On 10 000 $US a year for 30 years at 7%, traditional wins by 18 892 $US after tax. The account grows to 944 608 $US before any retirement tax — the traditional's 22% retirement tax is the swing factor.
Calculated in your browser. Compares equal contributions and assumes the traditional's up-front tax saving is invested. Uses flat marginal rates. Not tax advice.
Formulas and content last reviewed . IRS limits change each year — confirm current figures at IRS.gov and with your plan administrator.
The short answer
Roth vs traditional 401k comes down to your tax rate now versus in retirement. A Roth is funded with after-tax dollars and withdrawn tax-free; a traditional is pre-tax now and taxed on withdrawal. If your tax rate in retirement will be the same or higher than today, the Roth usually wins; if it will be lower, the traditional wins. For example, contributing $10,000 a year for 30 years at 7%, with a rate falling from 24% today to 22% later, leaves the traditional ahead by about $18,800; if your rate instead rose to 28%, the Roth would win by roughly $55,700. This calculator compares the after-tax value of both on identical contributions. One caveat: a fair comparison assumes you actually invest the traditional's up-front tax saving, and your employer's match is always pre-tax (traditional) regardless of which type you choose.
Formula & method
Roth = C·F vs Trad = C·F·(1 − Tr) + (C·Tc)·F
Both accounts grow at the same rate; the difference is when the tax is paid. F is the future-value growth factor.
Grow the contribution over your time horizon at the expected return.
Roth: the full balance is yours tax-free at withdrawal.
Traditional: subtract retirement tax from the balance…
…then add the invested value of the up-front tax deduction the traditional gave you.
Guide
The gross amount you would put into either account each year.
Your marginal rate today and your expected rate in retirement.
Your expected average return and the years until you withdraw.
The tool shows both after-tax values and the dollar difference.
Examples
Inputs
Result
When your rate drops in retirement, the traditional edges ahead — but only if you actually invest the up-front tax savings.
Inputs
Result
If you expect a higher rate later — common for high earners early in their careers — the Roth's tax-free growth wins clearly.
Methodology
Compares equal gross contributions, and assumes the traditional's up-front tax saving is invested in a taxable account (otherwise the Roth looks better than a fair comparison shows).
Uses flat marginal tax rates; real brackets are progressive and change over time.
The employer match is always pre-tax (traditional) regardless of which type you choose for your own contributions.
Ignores state tax changes, required minimum distributions and the taxable account's own drag on the invested tax savings.
Contribution limits, catch-up amounts, the early-withdrawal penalty and RMD rules follow the Internal Revenue Code as administered by the IRS, using the published figures for the 2026 tax year. Confirm current limits at IRS.gov, as they are adjusted annually for inflation.
Primary sources
Details
Roth 401k: pay tax now, withdraw tax-free after 59½ (account open 5+ years). No income limit, unlike a Roth IRA.
Traditional 401k: deduct now, pay ordinary income tax on every withdrawal.
Your employer's matching contributions are always traditional (pre-tax), even in a Roth 401k.
You can split contributions between both types in the same year, as long as the combined total stays under the deferral limit.
Roth 401k funds can be rolled to a Roth IRA to escape required minimum distributions entirely.
How it connects
Applications
Likely to earn (and be taxed) more later — the Roth's tax-free growth often wins.
In a high bracket today with a likely lower one in retirement — the traditional deduction can win.
Split across both to hedge against not knowing future tax rates.
Related tools
FAQs
It depends on your tax rate now versus in retirement. A Roth wins if your future rate is equal or higher, because you pay tax at today's lower rate and withdraw tax-free; a traditional wins if your rate will be lower later, because you deduct at today's higher rate. When rates are similar the difference is small. For example, $10,000 a year for 30 years at 7%, with a rate falling from 24% today to 22% later, leaves the traditional ahead by about $18,800; if your rate instead rose to 28%, the Roth would win by roughly $55,700. Many savers split the two to hedge future tax uncertainty. One caveat: a fair comparison assumes you actually invest the traditional's up-front tax saving — spending it erases its advantage — and your employer's match is always pre-tax regardless of which you pick.
Security & privacy
Uses the current IRS contribution limits, penalty rules and RMD tables — updated for 2026.
No signup, no email wall, no paywall. Every calculator is fully usable on first visit.
Every calculation runs client-side in JavaScript. Nothing is sent to a server or stored.
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The right choice can be worth tens of thousands of dollars over a career. Enter your numbers to see which account type leaves you with more after tax.