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Traditional 401(k) vs Roth calculator

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Employee elective deferral limit 2026: $24,500 (IRS). Catch-up age 50+: $8,000; ages 60–63: $11,250. Same paycheck cost: Roth contribution = traditional × (1 − tax now). State tax on contributions/withdrawals ignored. Investment return is a constant average.

15 thousand

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Roth looks better on these assumptions

$791,815

Traditional grows to $1,015,147 and leaves about $791,815 after 22%→22% tax. Roth costs the same today with a $11,700 contribution and finishes at $791,815 tax-free. Edge: $0. Limit used: $15,000 of $24,500 (2026).

Traditional after tax
$791,815
Roth (tax-free)
$791,815
2026 elective limit
$24,500

Federal income tax only on the model withdrawal; no state tax, RMDs, NIIT or employer match. Not advice.

Traditional vs Roth 401(k)

A traditional 401(k) lowers taxable pay today and taxes withdrawals later. A Roth 401(k) uses after-tax pay today and skips tax on qualified withdrawals.

This tool keeps your paycheck the same: the Roth contribution is smaller by today’s marginal rate, then both grow at the same return.

Limits follow the IRS 2026 tables. High earners may face extra catch-up Roth rules; those are not modelled.

Sources

What this calculator does not account for

  • State tax, employer match, RMDs and NIIT.
  • The special Roth catch-up rule for high earners.

How this is calculated

Formula: Same paycheck cost

Roth annual =Traditional annual × (1 − tax now); compare FV after tax later

What the symbols mean

  • TraditionalPre-tax contribution; withdrawals taxed at the retirement rate.
  • RothAfter-tax contribution sized so take-home matches; withdrawals tax-free.
  • LimitIRS elective deferral $24,500 in 2026, plus catch-up if age 50+.

Good to know

  • State tax, employer match, RMDs and NIIT are ignored.
  • If your retirement rate is lower, traditional often wins; if higher, Roth often wins.

Read the full methodologyFound an error? Contact us

Worked examples

Each example is worked out by the same code as the calculator above.

$15,000 traditional, 22% now and later, 25 years at 7%

Same tax rate → similar finish; small differences come from contribution sizing.

22% now, 32% later

Roth usually finishes ahead.

Embed this calculator

The frame shows the tool only.

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Questions

What is the 2026 401(k) employee limit?

$24,500 for elective deferrals, whether traditional or Roth. Catch-up is $8,000 from age 50, or $11,250 at ages 60–63.

Does this include my employer match?

No. A match is usually pre-tax in a traditional account; add it separately if you model it.

What about state tax?

Only federal marginal rates are modelled. Your state may tax traditional withdrawals or offer a Roth advantage.