Roth vs. Traditional Calculator
Compare Roth and Traditional the honest way — both equal-contribution and equal-cost framings, side by side — with the breakeven tax rate that actually decides it.
At equal tax rates the two are identical. Your breakeven retirement tax rate is 19.9% — retire above it and Roth wins; below it, Traditional does.
Same-cost framing: identical after-tax cost to your paycheck.
| Group | Roth | Traditional |
|---|---|---|
| Same contribution | $636,228 | $622,625 |
| Same cost to you | $636,228 | $636,228 |
Traditional's after-tax value falls as the retirement tax rate rises, crossing the flat Roth value at about 22% — your current tax rate.
Simplified: uses flat marginal rates, an annual contribution, and a 15% long-term capital-gains drag on the Traditional side account. Not tax advice.
For educational use only. This calculator provides estimates based on the assumptions you enter and does not constitute investment, tax, or legal advice. Results are not guarantees of future performance. Consult a qualified professional before making financial decisions.
How the Roth vs. Traditional calculator works
This tool answers one deceptively simple question: for the same effort, will you end up with more money by paying tax now (Roth) or later (Traditional)? The trap that sinks most calculators is comparing unequal contributions, so this one models two fair framings and shows both, because which one matches your situation changes how you should read the result.
In the same-contribution framing, both accounts receive the same gross dollars — the realistic case when you are contributing up to an IRA or 401(k) limit that applies equally either way. Here the Traditional saver has an advantage the naive comparison ignores: contributing pre-tax generates a tax deduction, and that refund is real money they can invest in a regular taxable account. We invest it for them and apply a capital-gains drag on its growth, which is what makes the comparison honest.
In the same-cost framing, both paths take the same amount out of your paycheck. Because a Roth dollar is post-tax and a Traditional dollar is pre-tax, keeping your out-of-pocket cost equal means the Traditional contribution is grossed up by your current tax rate. This is the cleanest apples-to-apples view, and it makes the core result unmistakable.
The punchline of both framings is the same and worth stating plainly: when your tax rate in retirement equals your tax rate today, Roth and Traditional produce identical after-tax wealth. The entire decision therefore rests on how your future rate compares to your current one.
The math, stated plainly
Let C be your annual contribution, r your return, and N the years to retirement. Contributions compound into a future value FV = C × ((1 + r)^N − 1) / r. Then, in the same-cost framing:
- Roth after-tax value =
FV(withdrawals are tax-free). - Traditional after-tax value =
FV ÷ (1 − taxNow) × (1 − taxRetire)— grossed up so the cost matches, then taxed on withdrawal.
Set those equal and the breakeven falls exactly at taxRetire = taxNow. Above it Roth wins; below it Traditional wins. The breakeven line chart shows Traditional’s after-tax value sliding down as the retirement rate rises, crossing the flat Roth line at your current rate.
Every input, explained
Annual contribution
What you put in each year. For an IRA, the same annual limit covers Roth and Traditional combined, so this is not a lever you can double by splitting. It scales both outcomes equally and does not change which account wins.
Current and retirement age
Together they set how many years your contributions compound. A longer horizon magnifies every dollar, but because it magnifies both accounts equally, it does not tilt the Roth vs. Traditional decision — it only raises the stakes.
Expected return
Your assumed average annual growth. Like the horizon, it scales both sides and is not the deciding factor. A higher return does make the tax-free nature of Roth growth more valuable in absolute dollars, which is a mild point in Roth’s favor.
Tax rate today
Your marginal rate — the rate on your next dollar of income, not your average rate. This is what a Traditional contribution saves you now, and it sets the breakeven. Be honest about it: use the bracket your last dollars fall into.
Tax rate in retirement
The single most important and most uncertain input. It depends on your future income, tax law decades from now, and where you live. Because it is a guess, try a range: if Roth still wins at a conservative low estimate, the case is strong.
Assumptions and limitations
- Flat marginal rates. Real tax is progressive; withdrawals may span several brackets, so a single rate is a simplification.
- No income limits or phase-outs. Roth eligibility and Traditional deductibility can phase out at higher incomes; this model ignores that.
- No RMDs, state tax, or benefit taxation. Required minimum distributions and state income tax can matter and are not modeled.
- Constant returns. A straight-line growth rate, not real market volatility.
- Not tax advice. A directional comparison to frame the decision, not a filing.
How this connects to the rest of your plan
This decision sits inside bigger ones. If you are deciding how much to put in your workplace plan and whether you are capturing the match, start with the 401(k) calculator. To see whether your overall savings are on track regardless of account type, use the retirement calculator. And if you simply want to build intuition for how contributions compound over decades, the compound interest calculator makes it vivid.
Frequently asked questions
- What is the real difference between a Roth and a Traditional account?
- It comes down to when you pay tax. Traditional contributions are made pre-tax and lower your taxable income today, but every dollar you withdraw in retirement is taxed as income. Roth contributions are made with money you have already paid tax on, and qualified withdrawals — including all the growth — are completely tax-free. Everything else about the two is secondary to that timing difference.
- Which one should I choose?
- The honest answer is a single comparison: your tax rate now versus your expected tax rate in retirement. If you expect to be in a higher bracket later, Roth usually wins because you lock in today’s lower rate. If you expect a lower bracket later, Traditional usually wins. When the two rates are equal, the outcomes are mathematically identical, so the choice is a wash and other factors break the tie.
- Why do so many online calculators get this wrong?
- Because they compare unequal things — putting the same gross dollars into each account without accounting for the fact that Roth dollars have already been taxed while Traditional dollars have not. A fair comparison must either hold the gross contribution equal (and let the Traditional saver invest the tax deduction) or hold your out-of-pocket cost equal. This calculator shows both framings side by side, and in both, equal tax rates produce an identical result.
- What is the breakeven tax rate?
- It is the retirement tax rate at which Roth and Traditional come out exactly even. On an equal-cost basis that breakeven is simply your current tax rate: retire in a higher bracket and Roth wins, a lower one and Traditional wins. Because a Traditional saver’s side investments face capital-gains tax, the breakeven tilts very slightly in Roth’s favor.
- Should I just split my contributions between both?
- Splitting — often called tax diversification — is a reasonable hedge when you genuinely do not know your future tax rate, which is most people. Having money in both gives you flexibility to manage your taxable income in retirement, for example by drawing from Traditional up to a bracket ceiling and topping up from Roth tax-free. It sacrifices a little expected value for meaningful certainty.
- Does the Roth vs. Traditional choice affect my contribution limit?
- No. For IRAs, a single annual limit applies to your combined Roth and Traditional contributions — you cannot double it by using both. The same is true within a workplace plan that offers both a Roth and a pre-tax 401(k). The choice is about tax treatment, not about how much you can save.
- Are there income limits on Roth contributions?
- Direct Roth IRA contributions phase out above certain income levels, while Traditional IRA deductibility can also phase out if you are covered by a workplace plan. High earners sometimes use a “backdoor Roth” to contribute indirectly. These rules change and are situation-specific, so verify the current thresholds and consult a tax professional before relying on them.
- What about required minimum distributions?
- Traditional accounts are subject to required minimum distributions (RMDs) starting at a set age, forcing taxable withdrawals whether you need the money or not. Roth IRAs have no RMDs during the original owner’s lifetime, which makes them useful for estate planning and for controlling taxable income later in retirement. This calculator does not model RMDs.
- Does this calculator account for state taxes or brackets?
- No — it uses a single flat marginal rate for today and one for retirement, entered by you. Real tax is progressive and varies by state, and your effective rate on withdrawals depends on your other income. Treat the result as a clean directional comparison, not a precise tax projection.
- If I expect the same tax rate, does the choice not matter at all?
- Mathematically the after-tax outcome is identical, but a few tiebreakers favor Roth: no required minimum distributions, tax-free flexibility in retirement, and protection against future tax-rate increases. Traditional’s edge is the certainty of a deduction today. When it is a wash on paper, those non-math factors decide it.