The leftover already on the site uses 22% now / 12% later: traditional $34,053.22 vs Roth $30,183.54. The leftover most 24% bracket stubs need is the same $10,000, 20 years, 7% return with 24% now.
Roth and traditional employee deferrals still share one 2026 cap: $24,500. The live tool compares the same gross dollars, not two different paycheck costs.
$10,000 deferred, 20 years, 7% return:
- 24% now and 12% later: traditional after tax $34,053.22, Roth $29,409.60. Traditional wins. Tax saved this year $2,400.
- 24% now and 24% later: both $29,409.60. Tie.
- 12% now and 24% later: traditional $29,409.60, Roth $34,053.22. Roth wins.
Traditional's $34,053.22 did not move from the 22% / 12% leftover. The retirement rate drives that column. Roth fell because you paid 24% on the way in, not 22%.
Run the Roth vs traditional 401(k) calculator →
Match first if the plan pays one: IRA vs 401(k). Hub: United States calculators.
Traditional $10,000 costs less on this year’s stub (FIT falls). Roth $10,000 is after-tax. The engine still grows $10,000 in both columns so the rate bet is isolated. Employer match is usually pre-tax even if you pick Roth. Estimate, not investment advice.
Direct answer: 24% → 12% favors traditional
- Growth factor = 1.07^20
- Traditional future value after tax = $10,000 × growth × (1 − 0.12) = $34,053.22
- Roth future value = $10,000 × (1 − 0.24) × growth = $29,409.60
- Gap: $4,643.62 in traditional’s favor
If the two rates are equal, the (1 − rate) term cancels and the columns match.
Traditional FV after tax = C × (1 + r)^n × (1 − retirement rate)
Roth FV = C × (1 − current rate) × (1 + r)^n
Checks you can re-run
| Deferral | Now | Later | Traditional after tax | Roth | Winner |
|---|---|---|---|---|---|
| $10,000 | 24% | 12% | $34,053.22 | $29,409.60 | traditional |
| $10,000 | 24% | 24% | $29,409.60 | $29,409.60 | tie |
| $10,000 | 12% | 24% | $29,409.60 | $34,053.22 | Roth |
Catch-up room is a different leftover: age 62 after $28,000 leaves $7,750. The $24,500 cap still applies to Roth and traditional combined.
What this is not
- A paycheck-cost compare. Traditional $10,000 lowers FIT this year. Roth $10,000 does not. The engine still seeds both columns with $10,000.
- Employer match math. Match is usually pre-tax even if you pick Roth. 50% of 4% on $96,000.
- State tax or NIIT. Those are out of this engine.
Because traditional grows the full $10,000 and is taxed at the later rate. 12% later is the same later rate as the 22% / 12% leftover. Only Roth changes when the current rate changes.
Yes. Combined employee elective deferrals. Catch-up is extra if the plan allows it.
It is a rate pair, not a forecast. If you expect the same rate later, the columns tie at $29,409.60. Confirm with a preparer. This is not investment advice.