Mega Backdoor Roth Estimator 2026
Find out how much extra you can contribute to your Roth 401(k) or Roth IRA beyond the standard $23,500 limit.
Last updated: May 2026
Standard 401k limit (Pre-tax + Roth).
Mega Backdoor Potential
Additional After-tax space
Requirement: Your 401(k) plan must allow "After-tax" (non-Roth) contributions and "In-service withdrawals/conversions" to pull this off.
Beyond the $23,500 Limit
In 2026, most people think they can only contribute $23,500 (or $31,000 if over 50) to their 401(k). However, the Total Section 415(c) Limit is much higher—typically around $72,000.
The Mega Backdoor Roth is a strategy that allows high earners to fill that gap (the difference between the total limit and their employee+employer contributions) using "After-tax" contributions, which are then immediately converted to Roth. This allows you to shield massive amounts of capital from future taxes.
How to use this calculator
- 1Employee Contribution — Enter your standard Pre-tax or Roth 401(k) contribution (max $23,500 in 2026).
- 2Employer Match — Input the total amount your employer contributes to your plan annually.
- 3Catch-up contribution — If you are 50 or older, the calculator automatically adds the $7,500+ catch-up room.
- 4Check Plan Documents — The 'Remaining' amount is your potential, but your plan must specifically allow After-tax contributions.
Formula & example
Mega Backdoor Space = Total Limit - (Employee Cont. + Employer Match)
Example: 35-Year-Old Engineer, $23.5k Cont., $10k Match.
- Total Limit: $72,000
- Used Space: $33,500
- Mega Backdoor Potential: $38,500
Benefits
Tax-Free Growth
Move tens of thousands of dollars into an environment where it will never be taxed again.
No Income Limits
Unlike a direct Roth IRA, the Mega Backdoor 401(k) path has no income phase-outs.
Early Retirement Path
A core strategy for the FIRE community to build a massive Roth ladder.
Use cases
Tech Employees
FAANG and large tech companies often have the most flexible 401(k) plans for this.
High-Income Surgeons
Maximizing tax-advantaged space after already filling backdoor IRAs and HSAs.
Business Owners
Setting up a Solo 401(k) to maximize their own personal Roth contributions.
Frequently asked questions
Is it legal?+
Yes, it is a perfectly legal tax strategy explicitly allowed by the IRS as long as your specific company plan supports it.
What is an In-service distribution?+
It's a rule that lets you move money out of your 401(k) and into an IRA while you are still working. It's the 'key' to the Mega Backdoor.
Can I do this with a Solo 401(k)?+
Yes, but you need a customized plan document that supports after-tax contributions (standard 'off-the-shelf' plans often don't).