The Roth vs Traditional IRA debate gets framed as a values question ("do you trust the government not to raise rates?") or a lifestyle question ("do you expect a high income in retirement?"). Those framings are real, but they obscure the more tractable version of the problem. The Roth vs Traditional choice is primarily a math problem with one central variable: your marginal tax rate now compared to your marginal tax rate in retirement.
Understanding exactly what that means, and how to find those two numbers, gives you a cleaner decision framework than most of the advice you will read.
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Marginal Rate, Not Effective Rate
The distinction between marginal and effective rate matters here. Your effective rate is the average rate you pay across all your income. Your marginal rate is the rate on your last dollar earned.
The Roth vs Traditional decision is about the marginal rate because IRA contributions reduce income dollar-for-dollar (Traditional) or grow tax-free dollar-for-dollar (Roth). If you contribute $7,000 to a Traditional IRA and your marginal rate is 22%, you save $1,540 in taxes this year. If you contribute $7,000 to a Roth IRA instead, you forgo that $1,540 deduction and pay tax on the contribution now.
The comparison is: save 22% now (Traditional), or save your withdrawal marginal rate later (Roth). If your withdrawal bracket is 22%, it is roughly equivalent. If your withdrawal bracket is higher, the Roth wins. If it is lower, the Traditional wins.
Finding Your Current Marginal Rate
Your marginal rate is the bracket your last dollar of taxable income falls into. For 2026, the marginal rate brackets for a single filer are approximately:
- Up to ~$11,900: 10%
- $11,900 to ~$48,400: 12%
- $48,400 to ~$103,350: 22%
- $103,350 to ~$197,300: 24%
- $197,300 to ~$250,525: 32%
- $250,525 to ~$626,350: 35%
- Over $626,350: 37%
If your taxable income (after the standard deduction) is $75,000, you are in the 22% bracket. That is the rate a Traditional IRA contribution saves you. The IRS retirement plans page publishes authoritative bracket tables and adjusts them for inflation annually.
Your effective rate, the rate you pay across all income, will be significantly lower because the lower brackets apply to lower portions of income. But the marginal rate is what drives the IRA decision.
Estimating Your Retirement Marginal Rate
This is the harder number. You are estimating what your taxable income will look like in retirement, before you know with certainty what that will be.
Sources of retirement income you need to count:
- Required minimum distributions from Traditional IRA and 401k accounts (start at 73)
- Social Security benefits (depending on total income, 0% to 85% is taxable)
- Any pension income
- Part-time or consulting income
- Capital gains distributions from taxable accounts
A common simplification is to assume your retirement income will be 70-80% of your pre-retirement income. In practice, this varies considerably. If you retire with $2 million in tax-deferred accounts, your RMDs alone may push $60,000-$80,000 in taxable income per year, keeping you in the 22% bracket even on a "modest" retirement.
If you have significant Social Security income on top of RMDs, the effective marginal rate on the Social Security portion can temporarily spike because of the provisional income calculation. Adding $1,000 of Traditional IRA withdrawal can cause $850 of previously untaxed Social Security to become taxable, creating an effective marginal rate higher than the stated bracket.
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When the Comparison Is Unclear
If your current and expected retirement marginal rates are within a bracket or two of each other, the comparison is genuinely uncertain. You are projecting the future, and tax rates themselves might change. Three strategies handle this:
Split contributions. You can put part of your $7,000 annual limit into a Roth and part into a Traditional. The combined limit still applies, but you can divide it in any ratio. This hedges the tax uncertainty without requiring a prediction you cannot make confidently.
Prioritize Roth when young. For workers in their 20s and early 30s, the very long compounding window for tax-free growth provides an additional benefit that skews toward Roth even when brackets are similar. The advantage compounds over 40 years in ways that are hard to fully price in a static comparison.
Use Roth for known low-rate windows. Years where your income drops temporarily (career change, sabbatical, early retirement before RMDs begin) are excellent times to contribute to a Roth or execute a Roth conversion, because you are locking in the low rate on money that will then compound tax-free.
Running the Numbers With a Calculator
Abstract bracket comparisons are useful for building intuition, but the actual dollar difference at retirement depends on your specific situation: your starting balance, years to retirement, contribution amount, and expected return rate.
The Roth IRA Calculator at EvvyTools lets you enter your actual numbers and see the after-tax retirement balance side-by-side for Roth and Traditional. It runs the comparison at different return rates so you can see whether your choice is robust or sensitive to investment performance.
For the full explainer on how bracket comparison drives the Roth vs Traditional decision, the article Roth IRA vs Traditional IRA: Which Wins at Your Tax Rate? covers the framework end-to-end, including income limits, the 5-year rule, and the split-contribution approach.
Investopedia has solid, well-maintained reference pages for both the Roth IRA and Traditional IRA if you want a third-party overview of the rules before committing to a strategy.
The Decision Rule
In plain terms: if you are below the 24% bracket and do not expect significantly higher income in retirement, default to Roth. If you are in the 32% bracket or above, default to Traditional. If you are somewhere in the middle, run the numbers with your specific assumptions, split contributions, or both.
The one mistake to avoid is not choosing at all. Both accounts are dramatically better than a taxable brokerage for long-term retirement savings. The marginal tax rate comparison is important, but either choice made consistently over 30 years beats the "optimal" choice made inconsistently.
Updating the Decision Over Time
The Roth vs Traditional decision is not a one-time choice. It makes sense to revisit it each year as your income and marginal rate evolve. A worker who starts in the 22% bracket and gets promoted into the 32% bracket mid-career should reconsider whether the Roth is still the right default. Similarly, someone who shifts to part-time work or takes a sabbatical drops into a lower bracket temporarily, which can be an excellent window for Roth contributions or conversions.
Think of the annual IRA contribution decision as a bracket-informed choice, not a permanent preference. In years where your marginal rate is lower than normal, weight toward Roth. In years where it is higher, weight toward Traditional. Over a career with variable income, this flexible approach tends to produce a well-balanced mix of pre-tax and post-tax retirement assets.
The Roth IRA Calculator at EvvyTools lets you rerun the projection with your current year's inputs, making it easy to revisit the choice annually rather than setting it once and forgetting it. For current bracket tables and contribution limits, the IRS retirement plans page is the authoritative source and updates with each tax year.
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