Same investment, two different tax deals
Traditional and Roth IRAs hold the same investments and grow by the same market returns — the only real difference is when you pay tax on the money. Traditional contributions reduce your taxable income today, and you pay tax on withdrawals in retirement. Roth contributions come from money you’ve already paid tax on, and qualified withdrawals in retirement are entirely tax-free. Whichever one nets you more spendable money depends on a single question: is your tax rate higher now or in retirement?
Why the math above sometimes surprises people
If your tax bracket today matches your expected bracket in retirement, the two accounts produce the identical after-tax outcome for the same contribution amount — that’s not a coincidence, it falls directly out of the math. Roth pulls ahead when you expect to be in a higher bracket in retirement than you are now — common for younger earners early in their careers, or for anyone who expects retirement income (Social Security, pensions, RMDs, part-time work) to push them into a higher bracket than their current salary suggests. Traditional pulls ahead when you expect a lower bracket in retirement, which is the more common assumption for people already in peak earning years.
The “frees up today” line is doing real work
A Traditional contribution doesn’t just defer tax — it reduces this year’s tax bill by your contribution times your current bracket. The Statement above shows that dollar figure explicitly. Some people invest that freed-up cash separately, which improves Traditional’s real-world result beyond what a simple side-by-side balance comparison shows. This calculator compares the two accounts on equal contribution terms; it doesn’t assume you invest the tax savings elsewhere, which is a legitimate refinement if you’re disciplined enough to actually do it rather than spend it.
Why “I don’t know my future tax rate” isn’t a reason to skip this
Nobody can predict tax policy or their own income decades out with certainty, but that’s not a reason to default to indecision — it’s a reason to diversify. Many financial planners recommend holding both account types when eligible, giving you flexibility to draw from whichever one is more tax-efficient in a given retirement year based on your actual bracket at the time. Treat this calculator’s inputs as your best estimate, not a certainty you need to lock in for thirty years.
Using this calculator
Your current bracket is knowable — use our Take-Home Pay calculator to find it if you’re not sure. Your retirement bracket is a genuine estimate; a common starting assumption is that it’ll be similar to or somewhat lower than your working-years bracket, but adjust it if you have a specific reason to expect otherwise, like a pension or a lower cost-of-living retirement location.
This article is for educational purposes only and isn't legal, financial, or tax advice. See our Disclaimer for details.
