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Roth or Traditional 401(k)?

Roth or traditional 401(k): which leaves more after tax at the same cost to your paycheck? Every piece below can be linked to, so it opens in a window on your reader's screen, current as of the record. No form to fill in.

2026 law · Reviewed September 7, 2026 · The full page, with methodology and sources · the terms · All tools

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The yearly contribution, the two tax rates, the years, and the return in; the after-tax result of each account, the difference, and the break-even rate out. In a frame it carries no cookies, no tracking, and a visible link back to the methodology. Your site has to allow frames; most do. The link that opens it in a small window is on the professionals page.

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In plain words.
A traditional contribution skips tax today and pays it when the money comes out. A Roth contribution pays tax today and skips it later. If both cost you the same in take-home pay, they grow the same way, and the only difference is which tax rate applies. This tool grows both at the return and years you choose, taxes each at its rate, and shows what is left.
Why it matters.
Most plans now offer both, and the choice is made on every paycheck for decades. The answer is not which account is better but which rate is higher, yours today or yours in retirement, and that is a guess worth making with the arithmetic in view.
An example.
$10,000 a year at a 22% rate today and 12% in retirement, growing 25 years at 6%: the traditional account leaves about $37,768 after tax and the Roth, at the same take-home cost, about $33,477. The traditional account is ahead by about $4,292, and the two would tie at a 22% rate in retirement.
Where it stops.
Both rates are guesses, and the one in retirement is the guess that decides it. The tool uses one flat rate on the withdrawals, one return for both accounts, and no state tax difference between now and later. It does not invest the tax a traditional saver defers, and it does not know what the law will say in thirty years.

Everything here reads from one reviewed record, so a copied piece carries its year and its review date. When the law moves, the embed updates by itself; a copied table or chart keeps the year in its caption. Corrections are welcome through the contact page.