What Is a Traditional vs. Roth Calculator?

Traditional and Roth retirement accounts are two answers to one question: do you want to pay tax now, or later? A traditional contribution goes in pre-tax — the full amount is invested, but every withdrawal in retirement is taxed as income. A Roth contribution is made with after-tax money — a smaller amount goes in, but qualified withdrawals come out tax-free. This calculator runs both paths side by side with the same contribution budget, the same return, and the same number of years, then declares which one leaves you with more spendable money after taxes.

How It Works

The calculator takes an annual contribution measured in pre-tax dollars. On the traditional path, all of it is invested each year. On the Roth path, tax comes off the top first, and the remainder is invested:

Look closely and the growth factor F appears in both formulas — it cancels out. What actually decides the contest is which tax rate is smaller. If your retirement rate is lower than today’s rate, traditional wins; if it’s higher, Roth wins; if they match, it’s a dead tie. That’s the whole intuition, and the calculator simply puts dollar amounts on it.

Worked Example: 22% Today, 12% in Retirement

Say you set aside $6,000 of pre-tax salary a year for 30 years at a 7% return, paying 22% tax today and expecting 12% in retirement. The deposits compound to a pre-tax pot of about $566,765. The traditional account hands that pot to the tax man once, at 12%, leaving about $498,753. The Roth path invests only $4,680 a year after tax, growing to about $442,076 — all tax-free. Traditional wins by roughly $56,676, because the money was taxed at the cheaper rate.

Flip the assumption — say retirement taxes rise to 24% — and the traditional pot shrinks to about $430,741 after tax, and Roth wins by about $11,335. Same savings, same market; only the tax timing changed.

Why Many Savers Use Both

Nobody knows what tax rates will be in 30 years — Congress rewrites the brackets regularly, and your own income path is uncertain too. Splitting contributions between traditional and Roth builds tax diversification: in retirement you can draw from the pre-tax bucket up to the lower brackets and top up from the Roth without pushing your taxable income higher. Early-career workers in low brackets often lean Roth; peak earners expecting quieter retirements often lean traditional; many land somewhere in between.

Common Mistakes to Avoid

The classic error is comparing your average tax rate today against your marginal rate later — use marginal rates on both sides for the contribution decision. Second, ignoring an employer match: match dollars typically land in a pre-tax bucket regardless, and skipping a match to fund anything else is usually a losing trade. Third, forgetting state taxes, especially if you plan to retire in a different state. Finally, remember this model uses flat rates and steady returns — reality has brackets, RMDs, and market swings. It provides educational estimates only, not financial or tax advice; consult a qualified professional before choosing.

Frequently Asked Questions