Roth 401(k) vs 401(k): Traditional or Roth?

Most people pick the Roth box on their 401(k) enrollment form the way they pick a sandwich. That checkbox is a bet on your marginal tax rate, and for a high earner it moves six figures of lifetime tax. Whether you frame it as traditional vs Roth 401(k) or 401(k) vs Roth 401(k), it is the same decision. Here is the whole thing in one comparison.

A 401(k) is an employer-sponsored retirement plan that allows employees to contribute up to $24,500 in 2026 ($32,500 if age 50+) . The key decision is whether those contributions go to a traditional bucket, a Roth bucket, or both. Fewer than 30% of plans offer Roth 401(k) deferrals , but that is changing. If your employer does not offer Roth, consider a Backdoor Roth IRA strategy instead.

If your question is whether to fund the 401(k) or a Roth IRA first, that is a different decision: see 401(k) vs Roth IRA. Everything on this page applies to 403(b) plans with a Roth option too; the plan differences live at 403(b) vs 401(k). Have a 401(a) instead? See 401(a) vs 401(k) for how that plan type differs. And if you are deciding whether to fund a 403(b) or a Roth IRA first, that funding-order question is covered at 403(b) vs Roth IRA: the funding order.

Your employer may match contributions (commonly 3 to 4% of salary ). Match funds are always deposited to the traditional side by default, even if you elect Roth deferrals. That matters for Roth ladder planning.

Traditional 401(k) contributions reduce your taxable income dollar-for-dollar in the year contributed. If you earn $150,000 and contribute $24,500, you report only $125,500 of taxable income. This immediate tax deduction is powerful if you are in the 32% or 35% federal tax bracket .

Traditional 401(k) distributions are taxed as ordinary income in retirement. Required Minimum Distributions (RMDs) start at age 73 under current law . The IRS Uniform Lifetime Table divisor for age 73 is 26.5, which implies roughly a 3.77% first-year withdrawal rate , whether or not you need the money that year.

Roth 401(k) contributions are made with after-tax dollars, so there is no immediate income tax reduction. But all growth is tax-free, and qualified withdrawals (age 59.5+, 5-year hold) are never taxed . This is the opposite benefit: pay tax now, zero tax later.

Comparing the Roth 401(k) against a Roth IRA specifically? That is its own page: Roth 401(k) vs Roth IRA.

The power of a Roth 401(k) is compounding tax-free growth. Illustrative example: a 40-year-old contributing $24,500 annually for 25 years (retiring at 65) could grow the balance to roughly $1.3M, assuming a 6% annual return . Results vary. All of that growth, hundreds of thousands of dollars, is tax-free if the withdrawal is qualified.

Many plans, especially larger employer 401(k)s, allow in-plan Roth conversions. This means you can convert your existing traditional 401(k) balance, or future contributions, to Roth without leaving the plan or rolling to an IRA. The conversion is taxable in the year you convert, but the balance is Roth from that point forward.

We cover conversion mechanics, the pro-rata rule, and Form 8606 in our backdoor Roth and Roth conversion guide. Model your own conversion against the bracket edges with our Roth conversion calculator.

The Mega Backdoor Roth is a strategy for plans that allow after-tax contributions beyond your regular employee deferral, on top of the traditional-vs-Roth choice already covered above. If your plan allows it, you contribute after-tax dollars up to the plan's total limit, then convert those dollars to Roth, often with little or no additional tax owed on the conversion itself.

This fits physicians, dentists, and business owners whose plans permit after-tax contributions and in-plan conversions, and who have already maxed their regular deferral. Full mechanics, current-year limits, and the plan-document checklist live in our mega backdoor Roth guide; run your own numbers with the mega backdoor Roth calculator.

Not all plans allow Mega Backdoor conversions. Check your plan summary to confirm it permits (1) after-tax contributions, (2) in-plan Roth conversions, and (3) timely conversions, ideally the same pay period, to minimize taxable earnings on the converted dollars.

Most of our clients are physicians and high earners in the 32% or 35% bracket during their working years. For most of them, the honest answer is traditional now, convert later. Not because Roth is bad, but because the deduction at 35% today, followed by conversions at 22-24% in early-retirement gap years, beats paying 35% up front.

This is the modeling we do for high-income clients; we run this exact traditional-vs-Roth analysis in a free initial consultation.

The counter-case matters too. A young attending or resident who reasonably expects income to double in the next few years can pick Roth deliberately, locking in a low rate before it rises. And anyone whose employer match plus deferrals will build a very large pre-tax balance over a career should model the RMD tax shock below before assuming traditional wins by default.

State income tax changes the math too, and it can point either direction. If you work in a high-tax state and plan to retire in a no-tax state, deferring income now with a traditional contribution and paying tax later at a lower (or zero) state rate favors traditional, not Roth: you are pushing the state tax bill into a year when your state rate is lower. For example, working in New York (up to roughly 8.82% top state rate ) and retiring in Florida (0% state income tax) strengthens the case for traditional contributions today, since the state-tax portion of the deduction is captured now and the eventual withdrawal skips state tax entirely.

The Roth ladder (also called a "Roth conversion ladder") is a strategy to access converted funds before age 59.5 without penalty. In broad strokes: convert a slice of a traditional balance to Roth, pay the tax on the conversion, then wait 5 years. After that 5-year clock, the converted principal can be withdrawn tax-free and penalty-free, while any remaining balance keeps growing tax-free inside the Roth.

Sequencing conversions across low-income years is the core of our Roth conversion guide. The ladder is really a bridge concept: it's the mechanism that lets a traditional-now saver still end up with meaningful Roth money, on their own schedule, without paying the top bracket to get there.

This page is for W-2 employees and practice owners with a 401(k) or 403(b) that offers a Roth option, and who are deciding how to split contributions between the two. It is especially relevant for physicians and other high earners weighing a deduction today against tax-free income later.

You do NOT need this page if your plan has no Roth option; your comparison is 401(k) vs Roth IRA instead. You also don't need the analysis if your marginal rate is 12% or below ; just pick Roth and move on. The traditional-vs-Roth decision only gets genuinely interesting at 22% and up.