Roth vs. Traditional 401(k) Calculator · Generated September 26, 2026
Roth vs. Traditional 401(k) Calculator
Most 401(k)s aren't all one type — you likely have a Traditional balance, a Roth balance, or both, and you can split new contributions between them too. Enter your real numbers on both sides and see your actual projected after-tax total, plus whether your new contributions would do better going 100% Roth, 100% Traditional, or staying split the way they are now.
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Enter your real balances. These stay whatever tax type they actually are — Traditional always gets taxed on withdrawal, Roth never does — the calculator doesn't reassign them the way a simpler tool might.
Your projected total, after tax
Where the money comes from
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Every Traditional contribution reduces your taxable income, so it effectively puts money back in your pocket at tax time — this account models what happens if you invest that money instead of spending it.
How much tax does Roth save you??
This is your Roth balance × your retirement tax rate — the ordinary-income tax that money would owe if it were sitting in a Traditional account instead. Roth withdrawals are never taxed, so this is money you simply never pay.
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This is your Roth balance × your retirement tax rate — the ordinary-income tax that money would owe if it were sitting in a Traditional account instead. Roth withdrawals are never taxed, so this is money you simply never pay.
Should new contributions go all-Roth or all-Traditional instead?
Holding your existing balances fixed, here's what the same $9,000/year in new contributions would be worth if all of it — instead of your actual split — went to one side.
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Existing balances get taxed the same way under both 100%-Roth and 100%-Traditional, so they cancel out of this comparison algebraically — only your new contribution and the tax savings it generates affect where the breakeven lands.
Above this rate, new contributions do better as Roth. Below it, they do better as Traditional. Your existing balances don't affect this number — they're taxed the same way either way. Since you're investing the tax savings, this exactly equals your current tax rate — the textbook result.
The gap between Roth and Traditional, over time?
Plotted on its own scale, not squeezed against your full balance — so the gap is visible even when it's a small slice of a large total, or even zero when your tax rate doesn't change. For a fixed pair of tax rates, this line never crosses zero: whichever side is ahead at year 1 stays ahead every year after, only the dollar amount grows.
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Plotted on its own scale, not squeezed against your full balance — so the gap is visible even when it's a small slice of a large total, or even zero when your tax rate doesn't change. For a fixed pair of tax rates, this line never crosses zero: whichever side is ahead at year 1 stays ahead every year after, only the dollar amount grows.
The gap stays at exactly $0 every year, all 25 years shown — Roth and Traditional produce the same after-tax outcome for new money at every point along the way, not just at the end.
The true cost of contributing today?
Traditional contributions are deducted before tax, so the dollar amount you enter is the full pre-tax cost. Roth contributions come from money you've already paid tax on, so the same nominal dollar amount actually represents more of your paycheck.
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Traditional contributions are deducted before tax, so the dollar amount you enter is the full pre-tax cost. Roth contributions come from money you've already paid tax on, so the same nominal dollar amount actually represents more of your paycheck.
A dollar contributed to Traditional and a dollar contributed to Roth aren't equally expensive right now — Roth money is taxed on the way in, so it takes more of your paycheck to fund the same contribution.
This is exactly why the after-tax totals can tie even though only Traditional gets an upfront deduction — for the same nominal contribution, you're already committing more real income to Roth today.
After-tax value over time
A worked example
Say you already have $20,000 in a Traditional 401(k) and $5,000 in a Roth 401(k), you contribute $500/month Traditional and $250/month Roth going forward, with a $200/month employer match, invested at a 7% average annual return for 25 years, and you're in the 22% marginal tax bracket both today and in retirement. Your actual mix would be worth $856,150 after tax. If that same $750/month in new contributions had gone 100% to Roth instead, you'd have $856,150; 100% Traditional — assuming you invest the tax savings it generates — gets you the same $856,150. That's not a coincidence: since your tax rate doesn't change, the calculator's breakeven rate for new money comes out to exactly 22%, matching what you entered on both sides, no matter what you already have saved in either account. Move your expected retirement rate a few points in either direction and one side pulls clearly ahead — try it above with your own numbers.
How the winner changes with your tax rate
Holding a $500/month new contribution, 7% return, and a 22% current tax rate fixed, here's the all-Roth advantage — a negative number means all-Traditional comes out ahead — at three different guesses for your retirement tax rate. This table doesn't depend on any starting balance, since existing money is taxed the same way under both options:
| Retirement tax rate | 10 years | 20 years | 30 years |
|---|---|---|---|
| Lower in retirement (12%) | -$8,705 | -$26,198 | -$61,354 |
| Same in retirement (22%) | +$0 | +$0 | +$0 |
| Higher in retirement (32%) | +$8,705 | +$26,198 | +$61,354 |
$500/month new contribution, no employer match, 7% average annual return, 22% current marginal tax rate, tax savings invested. The middle row shows the breakeven case: when the retirement rate matches today's rate, the gap is exactly $0 no matter what you already have saved.
Methodology
The calculator tracks four balances monthly: your Traditional 401(k) (starting balance plus new Traditional contributions, always taxed as ordinary income on withdrawal), your Roth 401(k) (starting balance plus new Roth contributions, never taxed again), any employer match (always pre-tax, taxed on withdrawal regardless of how your own contributions are split), and — if you choose to invest rather than spend it — a side taxable account holding the tax savings your Traditional contribution generates each month (contribution × your current tax rate).
“Should new contributions go all-Roth or all-Traditional instead?” compares two alternative scenarios that redirect the same combined new-contribution total to one side, while leaving your existing Traditional and Roth balances exactly as entered. Because existing balances are taxed identically under both alternatives, they cancel out of the comparison entirely — algebraically, the breakeven retirement tax rate for new money only depends on the new contribution and the side account, never on what you already have. With tax savings invested, that breakeven always equals your entered current tax rate exactly — a mathematical identity, not a coincidence — which is why the breakeven card above doesn't move when you change your starting balances.
This calculator doesn't model state-specific tax rules, Social Security taxation, required minimum distributions, in-plan Roth conversions, or capital-gains tax on the side account's growth (which would modestly reduce Traditional's advantage in practice) — it only flags when your entered new contributions exceed the 2026 IRS elective deferral limit for the catch-up eligibility you select (see IRS Notice 2025-67).
Questions
What's the actual difference between a Roth and a Traditional 401(k)?
A Traditional 401(k) contribution reduces your taxable income this year, grows tax-deferred, and is taxed as ordinary income when you withdraw it in retirement. A Roth 401(k) contribution is made with money you've already paid tax on, grows tax-free, and comes out completely tax-free in retirement. Both share the same 2026 IRS contribution limit — you can split contributions between the two if your plan allows it, but the combined total still can't exceed the limit.
Which one is actually better for my new contributions?
It depends entirely on whether your tax rate today is higher or lower than your tax rate will be when you withdraw. If the two rates are equal — and you invest the tax savings a Traditional contribution generates today rather than spending it — new contributions produce the exact same after-tax outcome either way. Above your current tax rate, Roth wins; below it, Traditional wins. The calculator above computes this breakeven point from your own numbers — and, perhaps surprisingly, it doesn't depend on what you already have saved, only on the new contribution itself.
Does my existing balance affect which one is better for new contributions?
No — and this surprises people. Money you've already saved is taxed the same way under both "all new money to Roth" and "all new money to Traditional" scenarios, since neither one touches it. Algebraically, it cancels out of the comparison completely. Your existing Traditional and Roth balances absolutely affect your total projected balance (that's why the calculator asks for them), but they don't shift the breakeven tax rate for where your next dollar should go.
Can I move money between my existing Traditional and Roth balances?
Not by just changing your contribution election going forward — that only affects new money. Moving existing Traditional dollars to Roth requires an in-plan Roth conversion, which is itself a taxable event: you pay ordinary income tax on the converted amount in the year you convert. This calculator doesn't model conversions; it only compares how to direct new contributions given the balances you already have.
Does my employer's match go into my Roth 401(k) if I contribute to Roth?
Usually not. Under most plans, employer matching contributions land in a separate pre-tax sub-account regardless of how your own contributions are split between Roth and Traditional — so that money is still taxed as ordinary income when you withdraw it. (Since SECURE 2.0, some plans now let employers offer a Roth match instead, but pre-tax remains the default almost everywhere.)
What are the 2026 401(k) contribution limits?
The 2026 employee elective deferral limit is $24,500. If you're age 50–59 or 64 or older, you can add a $8,000 catch-up contribution. If you're 60–63, a larger "super" catch-up of $11,250 applies instead. These limits apply to your own contributions, Roth and Traditional combined — employer contributions don't count against this particular limit, though a separate, much higher combined employee-plus-employer cap does apply.
Is there an income limit on Roth 401(k) contributions, like there is for a Roth IRA?
No — this is one of the most common points of confusion. A Roth IRA phases out at higher incomes, but a Roth 401(k) has no income limit at all. Anyone whose employer plan offers a Roth 401(k) option can contribute, regardless of income, which is exactly why the mega backdoor Roth strategy exists for high earners shut out of a Roth IRA directly.
Can I withdraw my Roth 401(k) money early without tax or penalty?
Less easily than you might expect from a Roth IRA. Roth IRA contributions can be withdrawn any time, tax- and penalty-free — but a Roth 401(k) doesn't offer that same carve-out. Withdrawals come out as a pro-rated mix of contributions and earnings, and the earnings portion stays taxable (plus a 10% penalty before age 59½) until you meet a "qualified distribution": the account open 5 years and you're 59½ or older (or disabled, or it's after your death). This is a big part of why people roll a Roth 401(k) into a Roth IRA at retirement or a job change — the Roth IRA's access rules are simpler.
What if I have no idea what my tax rate will be in retirement?
Nobody knows this for certain, which is why many people split contributions between Roth and Traditional to hedge against being wrong in either direction — sometimes called "tax diversification." As a rule of thumb: if you're early in your career and likely to earn (and be taxed) more later, Roth tends to look better. If you're in your peak earning years now and expect a lower-spending retirement, Traditional tends to look better.
How much tax will I actually avoid by having money in Roth?
Your Roth balance × your expected retirement tax rate — that's the ordinary income tax that money would owe if it were sitting in a Traditional account instead, and that you simply never pay because it's Roth. The calculator above charts this growing every year, not just as a single number at the end, since it compounds the same way your balance does.
If a Roth and a Traditional contribution can produce the same after-tax total, why would anyone pick Traditional?
Because the two options aren't equally expensive to fund today. A Traditional contribution is deducted before tax, so the dollar amount is the full pre-tax cost. A Roth contribution comes from money you've already paid tax on, so funding the identical dollar amount actually requires more of your paycheck. When the after-tax totals tie, it's not a coincidence — you've implicitly committed more real income to Roth to get there. Traditional can still make sense if you expect a lower tax rate in retirement, need the deduction to lower this year's tax bill, or simply can't spare the larger paycheck hit Roth requires today.
Is this financial or tax advice?
No. This calculator is for general educational purposes only, using simplified assumptions — flat tax rates you enter, no state-specific rules, no Social Security or RMD modeling, and no capital-gains tax on the side account that holds Traditional's invested tax savings. It isn't personalized financial, tax, or legal advice — see our Terms of Use for details.
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