Calculators·2026 limits
Mega backdoor Roth room
Your 401(k) has a much bigger limit than the $24,500 most people know about. If your plan allows after-tax contributions, the gap can be filled and moved into a Roth. This shows how big that gap is for you in 2026.
After-tax room in 2026
$0
- Overall limit for you
- Your 401(k) contributions
- Your employer's
- Plan's after-tax cap
- Per paycheck (26 a year)
- Catch-up you can add on top
Ask HR or check the plan document
- Does the plan take after-tax contributions? That's a separate bucket from Roth 401(k) contributions, and plenty of plans don't offer it.
- Can the after-tax money get to a Roth while you still work there? Either an in-plan Roth conversion (moving it to the Roth side of the 401(k)) or an in-service withdrawal to a Roth IRA. And can it happen automatically, ideally soon after each paycheck?
- Does the match "true up"? If you hit the $24,500 early in the year, some plans stop matching for the rest of it unless they make it up at year end.
- Are you a highly compensated employee? For 2026 that generally means you own more than 5% of the company or this employer paid you more than $160,000 in 2025. Plans have to pass a test (the ACP test) showing higher earners don't put in a lot more than everyone else, and when it fails, part of your after-tax money can be refunded.
- How fast does it convert? Anything the after-tax money earns before it's converted is taxable when it's converted.
How the math works
The IRS caps the total that can go into your 401(k) accounts at one employer each year. For 2026 that's $72,000, or 100% of your pay from that employer if that's less. The cap (section 415(c), if you want to look it up) counts your own pre-tax and Roth contributions, everything your employer puts in, and after-tax contributions. Catch-up contributions don't count toward it.
Most people only use part of that: their own contributions plus a match. The mega backdoor Roth fills the rest with after-tax contributions, then moves that money into a Roth, either inside the plan or out to a Roth IRA. Once it's in a Roth, the growth can come out tax-free in retirement.
So the room is the overall limit, minus your regular contributions (up to $24,500), minus your employer's. If your plan caps after-tax contributions at a percent of pay, the room is the smaller of the two. Plans can only count the first $360,000 of pay for 2026.
With the default numbers: $72,000 − $24,500 − $7,500 = $40,000 of room, or about $1,538 a paycheck if you're paid every two weeks.
Catch-ups and two jobs
If you're 50 or older by the end of 2026, you can add $8,000 of catch-up contributions on top of the $24,500, or $11,250 if you turn 60, 61, 62 or 63 in 2026. They don't count toward the $72,000, so they don't eat into your after-tax room. New for 2026: if your 2025 FICA wages from this employer were over $150,000, your catch-up contributions have to be Roth.
The $24,500 limit is per person, across every plan you're in. The $72,000 limit is per employer, so a plan at a second, unrelated employer has its own.
What this leaves out
Your plan's own rules, which matter more here than anywhere else in a 401(k): whether it allows after-tax money at all, its caps, how often it converts and how it handles the nondiscrimination tests. It also leaves out forfeitures that get added to your account, 403(b) and 457 plans, and solo 401(k)s for the self-employed, which have their own math. If you switched jobs this year, enter only this employer's pay and contributions. The $24,500 still counts what you put in at both jobs, so you may have less of it left here.
And it's the plan's year-end numbers that count. If the match is figured per paycheck, maxing out early can cost you match money unless the plan trues up.
Watch
- Mega Backdoor Roth (Step by Step) (from 2024, so the dollar limits in it are older; the steps still hold)
- Backdoor Roth IRA Explained (Step by Step Process)
Sources: IRS: COLA increases for dollar limitations (2026: $72,000, $24,500, $8,000, $11,250, $360,000, and the $160,000 highly compensated employee threshold), IRS Notice 2025-67 (the 2026 limits), IRS: 401(k) contribution limits (the lesser of $72,000 or 100% of pay, catch-ups outside it, one employer and related employers), 26 U.S.C. § 415(c) (employee contributions count as annual additions), IRS: Catch-up contributions (ages 60 to 63, and Roth catch-ups above $150,000 of prior-year wages starting in 2026), IRS: Designated Roth account FAQs (in-plan Roth rollovers of after-tax money, taxed on value minus basis) and the IRS 401(k) fix-it guide on the ADP and ACP tests.
Last checked against these sources on Nov 9, 2026.
An estimate for learning, not tax advice. I'm a CPA, but I'm not your CPA, and your plan document has the final word. Nothing you type leaves your browser. Full disclaimer.