Roth IRA vs Roth 401k
A Roth IRA is an individual account with an open investment menu and a smaller annual cap. A Roth 401k is the workplace version, often with an employer match and a fixed fund menu, so the tax timing is identical and the container is what differs.
Two accounts with the same tax treatment in different containers. Everything interesting here is about the container rather than the tax, which is unusual for a comparison of retirement accounts.
What each one is
A Roth IRA is an individual account. You open it, choose the provider, and hold almost anything that platform offers. Roth IRA covers it.
A Roth 401k is the workplace version. The employer chooses the provider and menu, and many plans add a matching contribution. The Roth 401k covers it.
The tax timing is the same in both. Contributions are made after tax and growth is sheltered, which removes the argument that dominates most account comparisons.
Where they differ
Who chooses the investments. An open platform against a fixed plan menu. That decides what the cheapest available fund costs, which compounds for decades.
Whether an employer adds money. Only the workplace version can carry a match, and where one exists it is the largest single difference between the two.
How much fits in. The workplace cap is usually the larger of the two, and both change over time, so the current figures are something to look up.
Whether income affects eligibility. The individual account can be restricted by income in ways the workplace one is not, which sometimes removes the choice entirely.
Where they agree
The tax treatment is the same. Both take after-tax money and shelter the growth, so nothing on this page turns on forecasting your future rate.
Both are eaten by costs identically. On this site’s arithmetic a 5-basis-point annual drag removes 1.5% of a thirty-year pot, 20 removes 5.8%, 75 removes 20.2% and 150 removes 36.5%.
Both are containers. Neither is an investment, and what you hold inside decides almost all of the outcome.
And both sit through drawdowns. On this site’s shared series 95% of bars sat below a prior peak and the longest recovery took 73 bars.
Which one to use
Contribute to the workplace version at least to the match. It is the only part of this comparison that is not a trade-off, because the money exists only in response to a contribution.
Use the individual account after that when its menu is cheaper. Being able to hold a very low-cost broad fund directly is worth real money across thirty years.
Use the workplace version when you want to contribute more. Its cap is usually the larger one, so it is where additional sheltered money can go once the individual limit is reached.
And use both when you can. They are not alternatives, and the order — match, then cheapest menu, then remaining capacity — covers almost every situation.
Why the menu outweighs the wrapper here
Because the tax question is already settled. With both accounts on the same treatment, the fund cost is the largest remaining variable and it is entirely under your control.
And because the difference compounds. Moving from 75 basis points to 20 keeps 14.4% more of a thirty-year pot on this site’s arithmetic, which dwarfs most container-level decisions.
What to check in each
Whether a match exists and what it requires. The contribution rate that receives it in full is the first figure to find, and it belongs to the workplace version only.
The cheapest broad fund in each menu. Not the default — the cheapest, and its annual cost.
Both current caps, and your eligibility. They differ, they change, and income can affect one of them.
And any account-level charge. Plans and providers both sometimes add one, stacking on top of fund fees.
Why having both is the usual answer
The caps are separate. Filling one does not consume the other, so somebody contributing seriously will reach the individual limit and still have workplace capacity available.
They cover different weaknesses. The workplace version supplies the match and the larger cap; the individual one supplies the open menu. Neither covers both.
Rolling between them is possible but not free. Moving money later involves paperwork and sometimes a period out of the market, which is a cost that does not appear in any comparison table.
And the split can change with a job. A new employer means a new plan, a new menu and possibly no match at all, which is worth remembering before treating today’s arrangement as permanent.
The original data
Of the 24,971 unique videos in research/search-study-corpus.jsonl, no title compares these two
directly — this pair is constructed from two subjects the corpus covers separately. Separately, the
Roth IRA appears in 24 titles at a median of 95,293 across 15 channels, and the Roth 401k in just 2 at a
median of 285,738 across 2. The counts come from site/corpus_count.py.
24 videos on one and 2 on the other. Twelve times the coverage for the individual account, and the workplace version’s median of 285,738 rests on two uploads — a figure that describes those videos rather than the subject.
The answer to the question on that chart is whichever menu is cheaper. The tax treatment is identical, so the fund cost is the deciding number — and it is one you can look up in a few minutes.
When it fails
The failure is treating this as a tax decision and never checking the fund costs. Time goes into comparing wrappers whose tax treatment is the same, while the workplace default fund sits at a charge nobody has examined. On this site’s arithmetic the difference between a 5-basis-point and a 75-basis-point fund is 18.7% of a thirty-year pot — larger than anything the container choice can deliver, and available immediately.
The second failure is missing the match while optimising the menu. Take the match first.
A third is assuming income limits do not apply. They can rule the individual account out.
A fourth is holding the default fund unexamined. Defaults vary widely.
A fifth is treating either as an investment. Both are containers.
And a sixth is assuming the caps stay put. They change over time.
Related
Roth IRA covers the individual account. The Roth 401k covers the workplace version. And the 401k covers the pre-tax version of the same plan.
The tax argument people spend so long on is already settled here — both are the after-tax version. What is left is the match, the menu and the cap, which are three concrete things you can look up this afternoon.
— Michael Whitman
This page is educational, not financial advice. Test every idea on your own charts before risking money.