Retirement
How the mega backdoor Roth works in 2026
Most people know the $24,500 elective deferral limit for 2026. Far fewer know that the total that can flow into your 401(k) from all sources — your deferral, employer match, and after-tax contributions — is the much larger section 415(c) limit of $72,000 ($80,000 if you are 50+, $83,250 at ages 60–63). The mega backdoor Roth fills the gap between those two numbers with after-tax dollars, then converts them to Roth.
The two-step move
It only works if your plan allows two things: (1) after-tax (non-Roth) contributions, and (2) either in-plan Roth conversions or in-service withdrawals to a Roth IRA. You contribute after-tax money up to the 415(c) ceiling, then promptly convert it to Roth so future growth is tax-free. Converting quickly keeps taxable earnings near zero.
| 2026 limit | Under 50 | Age 50–59 / 64+ | Age 60–63 |
|---|---|---|---|
| Elective deferral (§402(g)) | $24,500 | $32,500 | $35,750 |
| Total additions (§415(c)) | $72,000 | $80,000 | $83,250 |
Catch-up for 50+ is $8,000 ($11,250 at ages 60–63). Source: IRS Notice 2025-67. This tool measures after-tax room = total limit − your deferral − employer contributions.
Why it is worth the effort
Roth dollars grow and come out tax-free in retirement, with no required minimum distributions during your lifetime. For high earners locked out of direct Roth IRA contributions, the mega backdoor can move tens of thousands per year into the most tax-advantaged account available. Stack it with the smaller backdoor Roth IRA, and decide between Roth and pre-tax saving with the Roth vs traditional 401(k) calculator.
See the paycheck impact of your base deferral with the 401(k) contribution calculator, and if you are also doing large Roth conversions, the Roth conversion tax calculator.
Questions
Mega Backdoor Roth Calculator 2026 FAQ
What is the mega backdoor Roth limit for 2026?
It is the gap between the $72,000 total section 415(c) limit (under 50) and the sum of your elective deferrals plus employer contributions. For example, if you defer $24,500 and get $6,000 of match, your after-tax mega backdoor room is $41,500. The total limit rises to $80,000 at 50+ and $83,250 at ages 60–63.
Does my 401(k) plan need special features?
Yes. Your plan must permit after-tax (non-Roth) contributions and must allow either in-plan Roth conversions or in-service distributions to a Roth IRA. Without both pieces, the strategy is not available, regardless of the IRS limits. Check your plan documents or ask HR.
Is the mega backdoor Roth taxed?
Your after-tax contributions are made with already-taxed dollars, so converting the principal is tax-free. Only investment earnings that accrue between contribution and conversion are taxable, which is why people convert quickly — ideally before any meaningful growth occurs.
Can I do the mega backdoor and a regular backdoor Roth?
Yes. They use different accounts and limits. The mega backdoor uses after-tax 401(k) space up to the $72,000 415(c) limit; the regular backdoor Roth uses the $7,500 IRA limit. High earners often do both in the same year.
- Sources: IRS Notice 2025-67 (2026 §402(g) $24,500, §415(c) $72,000) · IRS COLA limitations table · IRC §§402(g), 415(c), 402A.
- 🔄 Last updated June 27, 2026 · Tax year 2026
Disclaimer: Educational estimate only — not financial or tax advice; the operator is not a financial adviser or CPA. Availability depends on your specific 401(k) plan. Confirm details with your plan administrator and a professional.
← Back to the full salary calculator · Related: Backdoor Roth · Roth conversion · Roth vs traditional 401(k) · 401(k) impact · Quarterly tax · Marginal rate