Your marginal tax rate is the tax bracket you pay on your last dollar of income, and it's the right number to use when deciding whether a Roth IRA makes sense for you

A marginal tax rate is not your overall tax rate. It's the percentage you pay on the next dollar you earn. If you're single and earn $50,000 a year, your marginal rate is the tax bracket that applies to that $50,000 — not an average of all the brackets below it. This matters for Roth decisions because you're comparing what you pay in taxes now against what you'll pay in taxes later.

The federal government uses seven tax brackets for 2024, ranging from 10% to 37%. Your bracket depends on your filing status and total income. If you're in the 22% bracket, that means the last portion of your income is taxed at 22%. When you contribute to a Roth IRA, you're paying tax at your marginal rate today in exchange for tax-free withdrawals later. If you expect to be in a higher bracket in retirement, a Roth usually makes sense. If you expect to be in a lower bracket, a traditional IRA might save you more.

Key Takeaways

  • Your marginal tax rate is the percentage you pay on your highest income, not your average rate across all brackets.
  • Roth contributions are made with after-tax dollars at your current marginal rate, so you benefit most if you expect higher tax rates in retirement.
  • You can find your marginal bracket by looking at the IRS tax tables that match your filing status and total income for the year.
  • If your income is rising or you expect to withdraw large amounts in retirement, a Roth IRA locks in today's lower rate and avoids future tax increases.

How marginal rate works with Roth contributions

When you put money into a Roth IRA, you don't get a tax deduction. You pay income tax on that money in the year you contribute it, at your marginal rate. If you're in the 24% bracket and contribute $7,000 to a Roth, you're essentially paying 24% in tax on that $7,000 right now. The trade-off is that the money grows tax-free, and you pay zero tax on withdrawals in retirement.

This is the opposite of a traditional IRA, where you get a deduction today (reducing your taxable income) but pay tax on withdrawals later. The Roth only makes financial sense if you believe your marginal rate in retirement will be equal to or higher than your rate today. If you're 30 years old, in the 22% bracket, and expect to be in the 24% bracket at 70, a Roth saves you money. If you expect to drop to the 12% bracket, a traditional IRA would have been better.

Finding your marginal tax bracket

The IRS publishes tax brackets every year. For 2024, the brackets are different depending on whether you file as single, married filing jointly, married filing separately, or head of household. You find your bracket by locating your total taxable income on the table that matches your filing status.

For example, if you're single with $60,000 in taxable income in 2024, you fall into the 22% bracket (the bracket covers income from $11,601 to $47,150 for single filers, so your income extends into the 24% bracket). Your marginal rate is 24% because that's the rate on the portion of your income above $47,150. The IRS website publishes these tables each January, and tax software will show you your bracket automatically when you enter your income.

When a higher marginal rate in retirement favors a Roth

You benefit most from a Roth IRA if you expect your marginal tax rate to rise by retirement. This happens in several real situations. If you're young and early in your career, your income will likely grow — meaning a higher bracket later. If you're self-employed and your business is growing, your future rate could be significantly higher. If you expect to have substantial investment income, rental income, or a pension in retirement, those add to your taxable income and push you into a higher bracket.

You also benefit if you think tax rates themselves will increase. Congress sets tax rates, and the current rates are scheduled to expire after 2025 under current law. If rates rise across the board, locking in today's rate with a Roth protects you from paying more later. This is speculative, but it's a legitimate reason some people choose Roth over traditional accounts.

When a lower marginal rate in retirement favors a traditional IRA

A traditional IRA makes more sense if you expect to be in a lower tax bracket in retirement. This is common if you're currently a high earner but plan to stop working and live on a modest amount. If you're in the 35% bracket now but expect to withdraw only $50,000 a year in retirement (putting you in the 22% bracket), a traditional IRA deduction saves you 35% today and costs you only 22% later — a 13-point gain.

This also applies if you plan to work part-time in retirement or have minimal other income. The key is comparing your marginal rate now to your expected marginal rate when you withdraw. If the number is lower later, traditional wins. If it's higher or the same, Roth wins or breaks even.

Income limits and how they interact with marginal rate

Roth IRA contributions have income limits that phase out your ability to contribute directly. For 2024, the phase-out range for single filers is $146,000 to $161,000 of modified adjusted gross income. If you're above that range, you cannot contribute directly to a Roth, though you may be able to use a backdoor Roth strategy (converting a traditional IRA to a Roth).

Your marginal rate is still relevant at high incomes because it tells you whether the conversion makes sense. If you're in the 32% or 35% bracket and converting a traditional IRA to a Roth, you'll owe tax at that rate on the conversion. You're paying a high price today, so you need to be confident that your retirement rate will be even higher, or that you won't need the money for many years to let the tax cost compound into gains.

Using marginal rate to compare Roth versus traditional side by side

Here's a concrete comparison. Suppose you're 35, single, with $75,000 in taxable income (putting you in the 22% marginal bracket). You want to contribute $7,000 to an IRA.

Roth route: You contribute $7,000 after paying 22% tax on it ($1,540 in tax). The $7,000 grows tax-free for 30 years. At retirement, you withdraw it tax-free.

Traditional route: You contribute $7,000 and deduct it, saving $1,540 in tax today. The $7,000 grows tax-deferred. At retirement, you withdraw it and pay tax at whatever your marginal rate is then. If it's 22%, you break even. If it's 24%, you lose. If it's 20%, you win.

The decision hinges entirely on whether you think your future marginal rate will be higher, lower, or the same. Your current marginal rate is the baseline you're comparing against.

Frequently Asked Questions

Is my marginal tax rate the same as my effective tax rate?

No. Your effective rate is your total tax divided by your total income — it's always lower than your marginal rate because you pay lower percentages on the first dollars you earn. Your marginal rate is what you pay on the last dollar. For Roth decisions, use your marginal rate, not your effective rate.

What if I'm not sure what my marginal rate will be in retirement?

If you're uncertain, a Roth is often the safer choice because it locks in today's rate and gives you flexibility. You can withdraw Roth contributions penalty-free if you need the money, and you're not forced to take distributions at age 73 like you are with traditional IRAs. The tax certainty is worth something even if you can't predict the future perfectly.

Does my marginal rate change if I contribute to a traditional IRA?

Yes, it can shift down slightly. A traditional IRA deduction reduces your taxable income, which can lower your marginal bracket. If you're near the edge of a bracket, the deduction might push you into a lower one. This is a small effect for most people, but it's another reason traditional IRAs can be valuable for high earners.

Can I use marginal rate to decide between Roth and traditional if I'm self-employed?

Yes, and it's especially important. Self-employed income is often higher and more variable than W-2 income. If your business is growing, your marginal rate will likely rise, which favors a Roth. If your business is stable or declining, a traditional IRA deduction might save you more. Calculate your expected income for the year to find your current marginal bracket, then estimate what you'll earn in retirement.

What if tax rates increase after I contribute to a Roth?

You're protected. Roth withdrawals are never taxed, regardless of what Congress does to tax rates. This is one of the main reasons people choose Roth — it's a hedge against future tax increases. You've already paid tax at today's rate, and no future rate change affects you.