The core trade-off
A traditional IRA gives you a deduction today and taxes every dollar you withdraw later. A Roth IRA gives you no deduction but every dollar comes out tax-free. Mathematically, if your tax rate is identical now and later, the two produce exactly the same result. The decision is entirely a bet on which rate is higher.
The fair comparison people skip
A traditional contribution is made with pre-tax money, so it also frees up a tax saving today. Comparing $7,000 into a Roth against $7,000 into a traditional without investing that tax saving quietly rigs the comparison against the traditional. This calculator invests it in a taxable account, with a drag applied for annual taxes on the gains.
Reasons Roth often wins in practice
- Most people do not invest the tax saving — they spend it.
- Roth IRAs have no required minimum distributions during the owner's lifetime, so the money can compound untouched.
- Contributions (not earnings) can be withdrawn at any time without tax or penalty, making it a partial emergency backstop.
- Tax-free income in retirement does not push up the taxable share of Social Security or trigger Medicare premium surcharges.
Reasons traditional can win
A peak earning year in a high bracket, especially in a high-tax state you plan to leave, makes the deduction genuinely valuable. Someone expecting substantially lower retirement income, or planning to leave assets to charity, also tends to favour pre-tax contributions.
Practical notes
Roth IRAs have income eligibility limits, though a backdoor conversion is a well-established route above them. Traditional IRA deductibility phases out if you are covered by a workplace plan. Contribution limits apply across both accounts combined. And converting traditional balances to Roth in a low-income year — early retirement, a career break — is one of the most reliable tax-planning moves available.