How this calculator works
The traditional contribution uses the full pre-tax budget and assumes it is deductible. The Roth contribution uses the same budget after current marginal tax. Contributions arrive at year end for the selected number of years, beginning now; the accounts then grow without deposits until retirement. Each balance funds level year-end withdrawals at the same effective return. Traditional withdrawals are taxed at the entered fraction; Roth withdrawals are assumed qualified. The annual budget is checked against the current-age 2026 IRA ceiling and held fixed. Eligibility, deduction phase-outs, future limits, early penalties and required minimum distributions are excluded.
Formula
Roth annual deposit = pre-tax budget x (1 - contribution tax rate). Retirement balance = annual deposit x ((1+r)^c - 1)/r x (1+r)^(years to retirement - c), using c at r = 0. Annual withdrawal = balance / ((1 - (1+r)^(-w))/r). Traditional take-home = withdrawal x (1 - retirement tax rate).
Worked example
Saving a $1,000 annual pre-tax budget for two years at 10% gives $2,100 in the traditional IRA. At a 20% contribution tax rate, the Roth receives $800 a year and reaches $1,680. Two years of withdrawals at 10% pay $1,210 gross from the traditional account and $968 from the Roth. At 25% retirement tax, traditional take-home is $907.50.
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Frequently asked questions
Is every traditional contribution deductible?
No. The comparison assumes full deductibility. Actual deductions depend on income, filing status and workplace-plan coverage.
Are the contributions equal?
They have equal pre-tax cost. The Roth deposit is lower because current tax is paid out of that same budget.
When are Roth withdrawals tax-free?
Qualified-distribution rules include age and account-holding requirements. This model assumes those conditions are met; it does not test them.