Roth vs Traditional Calculator: Pay Tax Now or Pay Tax Later?

At 24, Miguel Alvarez, now a network engineer in Denver, Colorado, had to pick Roth or traditional on his very first 401(k) enrollment form with no idea which one was “right” — the honest answer, it turned out, wasn’t about being right today, but about guessing correctly which tax bracket he’d be in decades from now. He picked Roth, and mostly forgot about the decision for twenty years. At 45, rolling a large traditional 401(k) balance into a Roth IRA after a job change, he assumed the money became instantly accessible tax- and penalty-free the moment it landed, the same way his original Roth contributions always had been. It doesn’t work that way, and the rule that says so is one of the most consistently misunderstood parts of the entire Roth system.

What the calculator actually compares

The same monthly contribution and growth rate run two ways — taxed on the way in but tax-free coming out (Roth), versus tax-deducted now but taxed as ordinary income on withdrawal (traditional) — showing the after-tax ending value both ways.

The same $500/month for 30 years can leave the Roth account ahead by roughly $40,000 in after-tax terms if your retirement tax rate ends up similar to or higher than today’s — the math flips in traditional’s favor if your retirement rate ends up meaningfully lower.

The bet, stated plainly

Roth wins if you expect to be in an equal or higher tax bracket in retirement than you are now. Traditional wins if you expect a meaningfully lower bracket in retirement — which is the more common assumption, but not a certainty, especially with decades until withdrawal and unknown future tax policy.

The five-year rule that isn’t just one rule

IRS Publication 590-B lays out two separate five-year clocks that most people conflate into one. The first covers a Roth IRA’s original contributions: the account must be open five years, and you must be 59½ (or meet another qualifying condition), before earnings can be withdrawn tax- and penalty-free. The second, less-known clock applies independently to every single Roth conversion: each amount converted from a traditional account starts its own five-year countdown before it can be withdrawn without a 10% early-distribution penalty, even if you’re already 59½ and even if your original Roth account has been open for decades. Miguel’s twenty-year-old Roth IRA didn’t give his brand-new conversion a pass — the converted balance had its own clock, starting fresh the day the conversion happened, completely independent of how long the account itself had existed.

The confusion is understandable: the account itself doesn’t change name or type when a conversion lands inside it, so there’s no visible marker distinguishing “old Roth money, fully clear” from “newly converted money, still on its own five-year clock.” A single statement shows one combined balance, and nothing on it flags which portion is which. Miguel had to go back through his own conversion paperwork to reconstruct the actual date his clock started, since the account’s overall opening date — the number he’d assumed mattered — turned out to be irrelevant to the specific dollars he wanted to withdraw.

Why splitting between both is a reasonable hedge

Since nobody can predict their exact future tax bracket or future tax law decades out, contributing to both traditional and Roth accounts creates “tax diversification” — flexibility to draw from whichever bucket makes more sense once your actual retirement tax situation is known.

Required Minimum Distributions — a quiet traditional-account catch

Traditional accounts require you to start withdrawing a minimum amount at a certain age, whether you need the income or not, forcing taxable income in years you might not want it. Roth accounts (for the original owner) don’t have this requirement, which matters for anyone who wants control over when income shows up — though a converted balance still sitting inside its five-year window is a reminder that “Roth” and “immediately unrestricted” aren’t the same word.

Run your own numbers, right here

YOU ENTER your monthly contribution, expected return, and years to retirement. IT TELLS YOU the after-tax ending value under each treatment — the comparison that decides whether Roth or traditional wins for your own numbers, separate from the five-year conversion clock that decides when a converted balance is actually touchable.

Frequently asked questions

Can I convert a traditional account to Roth later?

Yes, through a Roth conversion — but the converted amount is taxed as income in the year of conversion, so timing it in a lower-income year can reduce the tax cost of switching. Remember that each conversion also starts its own five-year penalty clock, separate from your original account’s age.

Which should a young, early-career saver generally favor?

Roth is often favored early in a career, when income (and tax rate) tends to be lower than it may be later — locking in today’s lower rate on contributions that then grow completely tax-free.

What actually happens if I withdraw a conversion before its five years are up?

If you’re under 59½ and withdraw the converted principal before its own five-year period ends, the withdrawal can trigger the 10% early-distribution penalty on that converted amount, even though it’s sitting inside a Roth account and even if your Roth IRA overall has existed for decades. Earnings on the conversion are subject to their own rules on top of that. Tracking each conversion’s individual date, not just the account’s opening date, is the only way to know which dollars are actually free to touch.

Why would anyone convert multiple times if each one starts a new clock?

This is exactly how the “Roth conversion ladder” strategy some early retirees use is built: converting a portion of a traditional balance every year, on purpose, so that a new five-year-cleared chunk becomes available each year going forward, creating a rolling supply of penalty-free money over time rather than one single five-year wait. It works precisely because each conversion’s clock is independent — the strategy is planning around the rule Miguel didn’t know existed, rather than being surprised by it.

None of this changes the core Roth-versus-traditional bet from earlier in this article — that’s still about guessing your future tax bracket correctly. The five-year conversion rule is a separate, mechanical layer on top: it governs timing, not which account wins on tax rate. Miguel’s twenty-year-old account being technically “Roth” gave him no shortcut around a rule that cares only about the date each dollar was converted, not the date the account itself was opened. Knowing the difference before converting a large balance, rather than after trying to withdraw it, is the five-minute check that would have saved him the confusion entirely — a single line in his own records noting the conversion date, checked against today, is all it takes — far cheaper than an unexpected 10% penalty on money he already assumed was fully his to use.

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Source: IRS Publication 590-B, distributions from individual retirement arrangements, five-year rules for Roth contributions and Roth conversions, at irs.gov.

Disclaimer: This article is for general information only and is not tax or financial advice. “Miguel Alvarez” is a composite character with invented finances, not a real person. Consult a qualified advisor before making retirement account decisions.