Sources verified · May 18, 2026

Roth or Traditional? The tax math, both sides.

Pick the comparison — same contribution or same take-home cost — and we show what each costs you this year and what each delivers at retirement under YOUR assumed future bracket, editable so the comparison stays honest. Sources cited.

Used to find your current marginal tax bracket.

On the Roth side, this is what you defer. On the same-take-home basis, the Traditional side defers more for the same paycheck hit.

Same take-home cost is the more apples-to-apples comparison: a Traditional dollar costs less out-of-pocket, so the Traditional side can defer more for the same paycheck.

Employer match (optional)

100 = dollar-for-dollar, 50 = fifty cents per dollar. Leave 0 if you don't get a match.

The cap on the match, e.g. 4 means matched up to 4% of salary. Matched dollars are pre-tax on both sides.

Your future-bracket assumption (editable — drives the retirement-side math)

Your best-guess marginal federal bracket when you withdraw. Default 22% (a common middle-of-retirement assumption). Adjust to see the comparison shift.

Default 0% (moving to a no-income-tax state). Bump up if you plan to stay where your retirement-state taxes will apply.

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New here? See it work with example numbers:

What this tool does and doesn’t do

  • Does: a same-contribution OR same-take-home-cost comparison of Roth and Traditional 401(k) using IRS Pub 15-T 2026 federal brackets, per-state withholding for any state + DC, FICA 2026, an optional employer match, and your editable future-bracket assumption. Surfaces the implied current marginal rate, the retirement-side after-tax value, the 2026 elective-deferral cap, and the math case under your assumptions.
  • Doesn’t yet: investment-growth modeling (growth is identical under both inside a 401(k), so it cancels), employer-match vesting schedules and the §415(c) all-sources limit, Roth conversion ladder math, Social Security taxation thresholds, IRMAA Medicare premium surcharges, or city / local taxes.
  • This is bracket arithmetic, not a personalized recommendation. The right choice depends on assumptions only you can make — confirm important decisions with a qualified tax professional or fiduciary financial planner.