Daily Figures Edition No Sign-Up • Free Forever Vol. XII — No. 204
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Roth vs Traditional 401(k) Calculator

Compare the after-tax value of a Roth and a traditional 401(k) from the same pre-tax budget.

Filed by The Statistics Desk  |  Method: after-tax comparison
pre-tax dollars you can set aside
Better choice
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Which comes out ahead.
After-tax comparison
Roth 401(k) — net—
Traditional 401(k) — net—
Difference—
Pre-tax growth—
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How the Roth vs Traditional 401(k) Calculator Works

The choice between a Roth and a traditional 401(k) comes down to when you pay tax. With a traditional 401(k) you contribute pre-tax dollars, get the deduction now, and pay income tax on every dollar you withdraw in retirement. With a Roth 401(k) you contribute after-tax dollars — no deduction today — but qualified withdrawals, including all the growth, are completely tax-free.

To compare them fairly, this calculator starts from the same pre-tax budget. The traditional account invests the whole amount and is taxed at your retirement rate at the end. The Roth invests what’s left after paying today’s tax, then grows tax-free. The math shakes out to a simple rule: Roth wins if your tax rate is lower now than it will be in retirement; traditional wins if it’s higher now.

Traditional = grown × (1 − future tax)    Roth = (contribution − tax now) grown

Frequently Asked Questions

Is a Roth or traditional 401(k) better?

It depends on your tax rate now versus in retirement. If you expect a higher tax rate later, the Roth’s tax-free withdrawals win. If you expect a lower rate later, the traditional’s upfront deduction wins. Equal rates are a wash.

Why compare from the same pre-tax budget?

Because a dollar in a traditional 401(k) and a dollar in a Roth aren’t worth the same — the Roth dollar has already been taxed. Starting from the same pre-tax amount and taxing each at the right time is the apples-to-apples comparison.

Can I split contributions between both?

Yes. Many plans let you divide contributions between Roth and traditional, which hedges against not knowing your future tax rate. The combined limit still applies across both.

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