The Mega Backdoor Roth IRA is a retirement savings strategy that lets high earners contribute well beyond the usual Roth IRA and 401(k) limits—if their employer’s 401(k) plan allows after-tax contributions and rollovers/transfers of funds from their current employer’s retirement plan.
Use the Mega Backdoor Roth calculator below to estimate how much you could increase your portfolio value via this strategy. It’s a powerful way to build tax-free retirement savings, especially if you’re already maxing out traditional options.
Note: this calculator is for informational purposes only and does not constitute legal or tax advice.
How much additional money do you plan to contribute (in after tax-dollars) to your 401(k) each year? The 2025 maximum overall 401(k) contribution is $70,000. If your plan allows it, you can contribute additional after-tax funds to your 401(k) plan and roll these funds over to your Roth 401(k) or Roth IRA
What overall investment return do you expect to earn long-term?
How much do you believe your portfolio will yield in dividend income?
What is your overall capital gains tax rate? (include federal, state, ACA, etc.)
Your age now
Your age at retirement
Does your 401(k) plan allow Mega Backdoor Roth conversions?
| Hypothetical portfolio value at age after taxes from Mega Backdoor Roth Conversions | |
| Hypothetical portfolio value at age after taxes if you placed your money in a brokerage account | |
| How much you would hypothetically save in this example by using a Mega Backdoor Roth for (E9-E8) years |
Show Details
What is a Mega Backdoor Roth?
A Mega Backdoor Roth IRA isn’t a separate account—it’s a strategy. It allows you to contribute after-tax dollars to your 401(k), then convert that money into a Roth IRA. It’s “mega” because the contribution limits can be significantly higher than the usual Roth IRA limit of $7,000 per year.
Here’s how it works:
- In 2025, the total amount that can go into a 401(k) (including your contributions, employer match, and after-tax contributions) is $70,000.
- After you contribute the standard $23,500 and receive any employer match, you may still have room left up to the $70,000 cap. If you’re aged 50 or over, you can make an additional $7,500 in catch-up contributions.
- If your employer’s 401(k) plan allows after-tax contributions, you can use that leftover space.
- Later, you can convert those after-tax contributions to a Roth IRA—often while still working or after you leave your job.
Note that the Mega Backdoor Roth works differently from a Roth 401(k), which involves making after-tax contributions directly and is limited to $23,500 in 2025.
Who is this strategy for?
The Mega Backdoor Roth is ideal for:
- High-income earners who are already maxing out their traditional 401(k) and Roth IRA.
- People with extra cash flow who want to maximize retirement savings.
- Employees with access to 401(k) plans that allow after-tax contributions and in-service withdrawals or conversions.
If you’re unsure whether your plan supports this, ask your HR department for the plan’s Summary Plan Description (SPD) or speak to your benefits administrator.
