This calculator helps determine how much you can contribute to a Roth 401(k) after accounting for your regular 401(k) contributions and employer match. Your total tax-benefit contributions are subject to an annual IRS limit that must be followed.
Potential Mega Backdoor Roth Contribution (after-tax 401(k)) ($):
Annual Total 401(k) Contribution Including Employer Match ($):
Mega Backdoor Roth Calculator Instructions
The Mega Backdoor Roth 401(k) is a strategy that allows individuals to contribute significantly more to tax-advantaged retirement accounts than the standard limits. Here’s how it works and the key details you need to know:
Annual Total Contribution Limits of All Tax-Deferred and Tax-free Contributions
- For 2026, the total contribution limit to a 401(k) plan is $72,000 (or $80,000 for those over age 50). This total includes:
- All employee pre-tax 401(k) and Roth 401(k) contributions to regular or traditional 401(k) plans (up to $24,500 or $31,500 if over 50).
- All employer contributions or matches.
- All after-tax contributions to 401(k)s.
Note, the above includes all of your contributions, regardless of how many separate accounts you have.
Process for Mega Backdoor Roth
- Max out your pre-tax 401(k) and after-tax Roth 401(k) contributions: First, contribute the maximum allowed ($24,500 or $31,500 if over 50) to your 401(k) using pre-tax contributions.
- Make after-tax 401(k) contributions: Once you’ve maxed out your regular 401(k) contributions, you can make after-tax 401(k) contributions up to the overall $72,000 (or $80,000 if over 50) limit, including any employer contributions. Note: after the after-tax contribution to the regular 401(k), you can roll them over into a Roth 401(k), assuming a so-called in-service or in-plan distribution.
See Mega Backdoor Roth Savings Explained for more details.
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How to use the Mega Backdoor Roth Calculator
The Mega Backdoor Roth Calculator is designed to help you pressure-test 401(k) contributions, employer match capture, Roth versus pre-tax tradeoffs, and workplace plan decisions before you make a real-world change. Instead of relying on one rough estimate, run a few scenarios with conservative, base-case, and optimistic assumptions so you can see how sensitive the result is to returns, contribution levels, inflation, taxes, or timing.
A calculator result is most useful when you connect it to the account or plan decisions you actually control. After reviewing the output, compare it with your current savings rate, employer match rules, investment menu, expense levels, and withdrawal or rollover options. That is where MyPlanIQ’s plan pages and retirement research become useful companions to the raw number.
If the result looks weak, treat that as a planning signal rather than a dead end. Small changes such as contributing earlier in the year, capturing the full company match, lowering fees, adjusting withdrawal assumptions, or choosing a more suitable allocation can materially change long-term outcomes. Re-run the calculator after each change and use the related links below to keep moving from estimate to action.
Related resources
- Browse and compare retirement plans
- Read more about maximizing 401(k) match
- Explore all calculators
- 401k Calculator
- 401(k) Employer Match Calculator
Calculator FAQs
What 401(k) assumptions should you test?
Test your contribution percentage, employer match formula, salary growth, tax rate, and projected retirement date. Those are usually the inputs that drive the biggest differences in a 401(k) calculator result.
How should you compare Roth and traditional 401(k) results?
Look at your current marginal tax rate, likely retirement tax bracket, employer match structure, and how long the money has to grow. The better choice often depends on your specific tax timeline rather than a generic rule.
Why pair a 401(k) calculator with a plan page?
Your savings outcome depends on the real plan available to you. Pairing the calculator with a MyPlanIQ plan page helps you see fees, investments, and match details that a generic calculator alone cannot capture.
How to use the Mega Backdoor Roth Calculator
The Mega Backdoor Roth Calculator is designed to help you pressure-test 401(k) contributions, employer match capture, Roth versus pre-tax tradeoffs, and workplace plan decisions before you make a real-world change. Instead of relying on one rough estimate, run a few scenarios with conservative, base-case, and optimistic assumptions so you can see how sensitive the result is to returns, contribution levels, inflation, taxes, or timing.
A calculator result is most useful when you connect it to the account or plan decisions you actually control. After reviewing the output, compare it with your current savings rate, employer match rules, investment menu, expense levels, and withdrawal or rollover options. That is where MyPlanIQ's plan pages and retirement research become useful companions to the raw number.
If the result looks weak, treat that as a planning signal rather than a dead end. Small changes such as contributing earlier in the year, capturing the full company match, lowering fees, adjusting withdrawal assumptions, or choosing a more suitable allocation can materially change long-term outcomes. Re-run the calculator after each change and use the related links below to keep moving from estimate to action.
Related resources
- Browse and compare retirement plans
- Read more about maximizing 401(k) match
- Explore all calculators
- 401k Calculator
- 401(k) Employer Match Calculator
Calculator FAQs
What 401(k) assumptions should you test?
Test your contribution percentage, employer match formula, salary growth, tax rate, and projected retirement date. Those are usually the inputs that drive the biggest differences in a 401(k) calculator result.
How should you compare Roth and traditional 401(k) results?
Look at your current marginal tax rate, likely retirement tax bracket, employer match structure, and how long the money has to grow. The better choice often depends on your specific tax timeline rather than a generic rule.
Why pair a 401(k) calculator with a plan page?
Your savings outcome depends on the real plan available to you. Pairing the calculator with a MyPlanIQ plan page helps you see fees, investments, and match details that a generic calculator alone cannot capture.