Roth vs. Traditional Calculator (IRA & 401(k))
Enter your contribution, your tax rate today, and the rate you expect in retirement. You'll see the after-tax value of the Roth and traditional paths side by side, and which one your brackets favor.
The pre-tax amount you're deciding where to send
The rate your last dollar of income is taxed at today
The rate you expect on withdrawals later
After inflation. 5% is a common long-run assumption
Roth after-tax value
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Enter your contribution
Traditional after-tax value
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Winner
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One question: your bracket now vs your bracket later
Strip away the account names and a single comparison remains: the marginal tax rate you'd avoid by contributing traditional today, versus the rate you'll pay when the money comes out. Lower rate now than later favors Roth (pay the small tax today); higher rate now favors traditional (dodge the big tax today). Everything else, from paycheck mechanics to rollover rules, is downstream of that swap. Our Roth vs. traditional deep dive walks the full decision, including the eligibility wrinkles this calculator deliberately leaves out.
Why the math ties, and what breaks the tie in real life
At equal tax rates the two paths land on the identical dollar, which surprises almost everyone the first time. What breaks the tie is your income's shape over a lifetime. Most people earn (and are taxed) more in their peak working years than in retirement, which leans traditional. Early-career workers in low brackets are often the reverse: today's rate may be the lowest they'll ever see, which leans Roth. Add the genuinely unknowable, future tax law, and the honest answer is that you're making an educated bet either way, so make it with your real numbers: today's bracket is knowable, and your projected balance in the retirement calculator hints at how much taxable withdrawal income your future self might have.
Hedging with both
Since the bet can't be certain, splitting contributions between Roth and traditional buys flexibility instead of a prediction. In retirement, a year with heavy expenses can draw tax-free from the Roth side while lean years pull cheaply taxed traditional dollars, smoothing your effective rate across decades. If the deferral is happening inside a workplace plan, make sure the employer match is fully captured first, since that return beats either tax treatment. And whichever mix you choose, the balances live in different accounts that drift apart quietly, which is why Stoia shows Roth, traditional, and everything else as one net worth picture.
Frequently asked questions
What's the difference between Roth and traditional?
When the tax bill arrives. Traditional contributions skip income tax now and are taxed on withdrawal in retirement. Roth contributions are taxed now and withdrawn tax-free later. Same investments, same growth, opposite ends for the tax.
Why do Roth and traditional tie when tax rates are equal?
Because multiplication doesn't care about order. Contribution times growth times (1 minus tax) gives the same answer whether the tax haircut happens before the growth or after it. The winner is decided entirely by which rate is lower, not by when the tax is paid.
Which should I pick if I can't predict my future tax rate?
Split the difference. Holding both Roth and traditional money is called tax diversification: in retirement you can draw from whichever pot the year's tax situation favors. Many workplace plans let you split each contribution between the two.
Does this apply to both IRAs and 401(k)s?
Yes. The Roth-versus-traditional mechanics are the same in both account types; only the contribution limits and eligibility rules differ. The IRS sets those dollar limits each year and adjusts them, so check the current figures rather than relying on remembered numbers.
Doesn't traditional win because of the upfront tax deduction?
The comparison here already counts it. Traditional invests the full contribution precisely because the deduction leaves more to invest, while Roth invests the smaller after-tax amount. Framed this way, both choices cost your paycheck the same, and the deduction's advantage survives only if your retirement rate is lower than today's.
Does this calculator save my numbers?
No. Everything runs in your browser and disappears when you leave. Nothing is uploaded or stored.
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