Roth vs Traditional IRA: Which Wins Long-Term?

The Fundamental Tax Trade-Off

Both Roth and Traditional IRAs grow tax-free inside the account. The difference is when you pay tax:

• Traditional IRA: You contribute pre-tax dollars (deduction today), grow tax-free, pay ordinary income tax on every dollar you withdraw in retirement.
• Roth IRA: You contribute after-tax dollars (no deduction), grow tax-free, withdraw completely tax-free in retirement (contributions and earnings both), as defined in IRC §408A.

Neither is categorically better. The one that leaves you with more money after taxes is the one that applies the lower tax rate to the larger dollar amount. If your rate is higher now than in retirement, pre-tax (Traditional) wins. If your rate is lower now or equal, after-tax (Roth) wins or ties.

2026 Contribution Limits

Per Rev. Proc. 2025-32, the 2026 IRA contribution limit is $7,000 (under 50) or $8,000 (50 or older, catch-up).

Direct Roth contribution phase-out ranges (2026):

Above the phase-out end, you cannot contribute directly to a Roth IRA. You can still use the backdoor Roth strategy (see below).

When Traditional Wins

The Traditional IRA produces a better after-tax outcome when your current marginal tax rate is higher than your expected retirement marginal rate. This typically describes:

• High earners in their peak earning years (ages 45-60) who expect a meaningful income drop in retirement
• Workers near the top of the 24%+ brackets who expect Social Security + modest withdrawals to land them in 12-15%
• Anyone in a very high current marginal rate (32-37%) who has reason to expect a substantially lower retirement income

When Roth Wins

Roth wins when:

• Your current marginal rate equals or is lower than your expected retirement rate (common for workers under 40)
• You expect retirement income from Social Security, pension, and IRA withdrawals to push you into a bracket equal to or above your current one
• You value tax-rate uncertainty insurance — locking in today's known rate rather than betting on future tax law
• Estate planning is a priority — Roth IRAs pass to heirs without RMDs during the original owner's lifetime, and heirs enjoy 10 years of continued tax-free growth under current law
• You want flexibility — Roth contributions (not earnings) can be withdrawn penalty-free at any time

The Math: 40-Year Worked Example

Setup: 25-year-old contributor. $7,000/year contribution. 7% annual growth. Retires at 65 (40 years). Current marginal rate: 22%. Retirement marginal rate: three scenarios.

FV = 7,000 × [(1.07^40 − 1) / 0.07]
FV = 7,000 × [13.9745 / 0.07]
FV = 7,000 × 199.635
FV = $1,397,445 (Roth IRA ending value — entirely tax-free on withdrawal)

Tax savings reinvested: $1,540/yr for 40 years at 5% after-tax:
FV_savings = 1,540 × [(1.05^40 − 1) / 0.05]
FV_savings = 1,540 × 120.80
FV_savings = $186,032

Calculations assume annual contributions at start of year, all traditional withdrawals in one tax period at the stated rate, taxable savings account at 5% net after-tax return. Simplified; actual results will vary.

Backdoor Roth Strategy

High earners above the direct Roth MAGI phase-out ($165,000 single / $246,000 MFJ in 2026) can still fund a Roth IRA using the backdoor strategy:

1. Contribute $7,000 to a Traditional IRA — non-deductible (no deduction claimed, basis tracked on Form 8606)
2. Convert the Traditional IRA to Roth IRA — taxable only on the growth, if any

Pro-rata rule warning: If you have other pre-tax Traditional IRA balances, the IRS requires you to calculate the taxable portion of the conversion proportionally across all IRA balances. The pro-rata rule under IRC §408(d)(2) applies to all IRAs in aggregate.

The RMD Angle

Traditional IRAs require required minimum distributions (RMDs) starting at age 73 (rising to 75 by 2033 under SECURE 2.0, P.L. 117-328, Div. T §107). These mandatory withdrawals generate taxable income whether you need the cash or not.

Roth IRAs have no RMDs during the original owner's lifetime (IRC §408A). Use the RMD calculator to see what your Traditional IRA balance would generate in required distributions at age 73.

Frequently Asked Questions

Project Your Numbers with the Compound Interest Calculator

The 40-year table above uses simplified assumptions. Your contribution amount, growth rate, tax rates, and timeline all differ. The compound interest calculator lets you run your specific numbers, and the 2026 federal income tax calculator shows your current marginal and effective rates — the starting point for the rate comparison.