Roth vs. Traditional Calculator
Comparison assumptions
After-tax comparison
Under these assumptions, the Traditional path finishes with more after-tax value. This is a tax-timing comparison, not an account recommendation or eligibility determination.
What happens to the same pre-tax savings capacity?
The Traditional path receives the full $10,000 annual pre-tax budget. The Roth path receives $7,600 after the entered current marginal tax rate, a difference of $2,400 per year. Both contributions are modeled at year-end and earn the same entered return.
Roth annual contribution = pre-tax savings budget × (1 − current tax rate)
Traditional after-tax ending value = gross Traditional balance × (1 − future withdrawal tax rate)
Roth after-tax ending value = gross Roth balance
Over 30 years, the model contributes $300,000 to the Traditional account and $228,000 to the Roth account. The Traditional balance reaches $944,608 before the modeled $207,814 withdrawal tax. The Roth balance reaches $717,902 and is treated as tax-free at withdrawal for this comparison.
Future tax-rate sensitivity
Everything except the future withdrawal tax rate stays fixed. Positive differences favor Roth; negative differences favor Traditional.
| Future tax rate | Traditional after tax | Roth after tax | Roth minus Traditional |
|---|---|---|---|
| 14% | $812,363 | $717,902 | -$94,461 |
| 22% | $736,794 | $717,902 | -$18,892 |
| 24% | $717,902 | $717,902 | -$0 |
| 34% | $623,441 | $717,902 | $94,461 |
What this comparison assumes
The Traditional contribution is assumed to be fully pre-tax or deductible, and its modeled ending balance is assumed to be fully taxable at the entered future withdrawal rate. The Roth contribution is the after-current-tax equivalent of the same pre-tax savings budget, and its modeled ending balance is assumed to be available tax-free at withdrawal.
The calculator does not determine IRA or workplace-plan eligibility, contribution limits, deductibility, income phaseouts, qualified-distribution status, required minimum distributions, early-withdrawal penalties, employer matching, Roth conversion taxes, tax credits, state-versus-federal treatment, account fees, or changing tax rates during the saving period. If those details matter to your decision, this simplified comparison is only one input.
The break-even rate is not a forecast. Under this equal-pre-tax-budget model with identical returns and contribution timing, the tax-rate decision is the main difference: a higher modeled future withdrawal rate tends to favor Roth, while a lower modeled future withdrawal rate tends to favor Traditional.
Related planning tools
Use the Portfolio Monte Carlo Lab for uncertain return paths and dated goals, the Withdrawal Sustainability Lab for retirement spending risk, and the Investment Fee Drag Lab for fee assumptions.