Mega Backdoor Roth 2027 Eligibility Check Calculator
A mega backdoor Roth means making after-tax contributions to a 401(k) on top of your elective deferrals and then moving them to Roth, through an in-plan Roth conversion or an in-service distribution. It only works if your plan allows after-tax contributions and one of those two ways out. Dollar limits here are the 2026 figures from IRS Notice 2025-67, the latest published: $24,500 elective deferral and $72,000 total defined contribution limit. The 2027 limits have not been announced.
Plan Requirements
Two things must be true of your plan. First, it must allow after-tax contributions beyond your elective deferrals. Second, it must give those dollars a way into Roth: either an in-plan Roth conversion or an in-service distribution that you can roll over. If either piece is missing, the strategy is not available in that plan. Your Summary Plan Description or plan administrator can confirm both.
How the Room Is Calculated
For 2026 the limitation for defined contribution plans under section 415(c)(1)(A) is $72,000 (up from $70,000), and the limitation on elective deferrals under section 402(g)(1) is $24,500 (up from $23,500). Room for after-tax contributions = $72,000 − your elective deferrals − employer contributions. Example: $72,000 − $24,500 − $15,000 match = $32,500.
What Is Not Included
The calculator assumes you defer the full $24,500 and ignores catch-up contributions (the age-50 catch-up limit for 2026 is $8,000). It does not check plan-specific caps, nondiscrimination testing, or the tax on any earnings converted along with the after-tax contributions.
Source and Disclaimer
Dollar limits are for 2026. The IRS normally announces the next year's limits in the autumn; when the 2027 figures are published the room will change. Estimates only — not tax advice.
Source: IRS Notice 2025-67 — 2026 Amounts Relating to Retirement Plans and IRAs. Last updated: October 2026.