Roth 401k Calculator
Updated August 2026 — reflects the 2026 IRS contribution limits.
Roth or Traditional? It comes down to one thing: your tax rate now versus in retirement. Enter both below and see which leaves you with more after-tax money — compared fairly, for the same cost to your paycheck today.
How this calculator compares Roth and Traditional
A fair comparison holds the cost to your paycheck equal. A Roth contribution is after-tax, so $10,000 in a Roth reduces today’s take-home by the full $10,000. A Traditional contribution is pre-tax, so the same paycheck hit lets you put in more — which this tool accounts for before comparing after-tax results.
Here’s the trap in most head-to-head numbers: comparing the same contribution to both accounts flatters Roth, because it quietly ignores the extra tax you paid up front to fund it. This calculator fixes that. It takes your Roth contribution as the true out-of-pocket cost, works out the larger pre-tax amount that would cost your paycheck the same, grows both at your return, and only then applies tax.
The math is short. If your current rate is tnow, a Roth contribution of C costs the same take-home as a Traditional contribution of C ÷ (1 − tnow). Both grow to a future value; the Roth is withdrawn tax-free, while the Traditional is taxed at your retirement rate tret. Work it through and the Roth’s after-tax edge is exactly (1 − tnow) ÷ (1 − tret) — greater than 1 whenever your retirement rate is higher than today’s.
A worked example
Say you put $10,000 a year into a Roth for 30 years at 7%. That grows to about $944,600, all tax-free. For the same paycheck cost at a 22% current rate, you could instead put about $12,820 a year into a Traditional account, which grows to roughly $1,211,000 — but at a 22% retirement rate, after tax that’s about $944,600 too. Identical, because the rates match. Nudge the retirement rate to 30% and the Traditional’s after-tax value drops below the Roth’s; drop it to 12% and Traditional pulls ahead.
When Roth wins, and when Traditional wins
Roth tends to win if you expect a higher tax rate in retirement than you pay today — common for younger savers early in their careers, or anyone who expects tax rates to rise. Traditional tends to win if you expect a lower rate later, which is typical for high earners near their peak.
- Lean Roth if: you’re early-career with room to grow your income, you’re in a low bracket now, you expect tax rates to rise broadly, or you value tax-free flexibility and estate benefits later.
- Lean Traditional if: you’re a high earner near your peak, you expect to drop into a lower bracket in retirement, or the up-front deduction helps you afford to save more today.
- Consider splitting: many savers contribute to both to hedge an unknowable future — “tax diversification.” You don’t have to pick one forever; you can change your election year to year.
Two things the headline number leaves out on purpose. First, your employer match almost always lands in a pre-tax account regardless of your choice — free money either way, so capture it first. Second, a Roth’s tax-free withdrawals don’t count as income in retirement, which can matter for things like Medicare premiums and how your Social Security is taxed. Those are reasons some savers value Roth beyond the raw math.
Roth 401(k) contribution limits for 2026
Roth and Traditional 401(k) contributions share one combined limit. For 2026 you can defer up to $24,500 in total across both, rising to $32,500 at age 50 and $35,750 for ages 60 to 63. Unlike a Roth IRA, a Roth 401(k) has no income limit.
| Year | Under 50 | Age 50+ | Ages 60–63 |
|---|---|---|---|
| 2026 | $24,500 | $32,500 | $35,750 |
The limit is a ceiling on your contributions; an employer match sits on top of it, up to the combined $72,000 cap. Because a Roth 401(k) carries no income limit, high earners who are shut out of a Roth IRA can still build a Roth balance here. To see how any contribution grows to retirement with your employer match included, use the main 401k calculator.
Source: 2026 figures reflect the IRS contribution limits announced in November 2025.