Mega Backdoor Roth Calculator 2025

Personal Information

Current Age

Annual Income ($)

Filing Status

Current 401(k) Contributions

Traditional 401(k) ($)

2025 limit: $23,500

Roth 401(k) ($)

Available: $500

Employer Match ($)

My plan allows after-tax contributionsMy plan allows in-service withdrawals/conversions

Tax & Investment Assumptions

Current Tax Rate (%)

Retirement Tax Rate (%)

Years to Retirement

Expected Return (%)

Understanding the Mega Backdoor Roth

The mega backdoor Roth is an advanced retirement savings strategy that allows high earners to contribute significantly more to Roth accounts than traditional limits allow. By utilizing after-tax 401(k) contributions and converting them to Roth, you can save up to $47,000 extra per year (2025 limits) in tax-free retirement accounts.

How It Works

Max out your regular 401(k) contributions ($23,500 for 2025)
Make after-tax contributions up to the 415(c) limit ($70,000 total for 2025)
Convert after-tax contributions to Roth IRA or Roth 401(k)
Enjoy tax-free growth and withdrawals in retirement

Key Requirements

Your 401(k) plan must allow after-tax contributions (not all do)
Plan should permit in-service withdrawals or conversions
You need available income to fund after-tax contributions
Works best for those already maxing regular retirement accounts

2025 Contribution Limits

Employee Deferrals: $23,500 (traditional + Roth 401(k) combined)
Catch-up (50+): Additional $7,500
Total 415(c) Limit: $70,000 (includes all contributions)
Highly Compensated: $155,000 income threshold

Tax Benefits

Traditional 401(k)

Tax deduction now
Tax-deferred growth
Taxed on withdrawal
Required distributions at 73

Mega Backdoor Roth

No tax deduction
Tax-free growth forever
Tax-free withdrawals
No required distributions

Common Pitfalls to Avoid

Waiting too long to convert (creates taxable gains)
Confusing after-tax with Roth 401(k) contributions
Poor recordkeeping for tax reporting
Not verifying plan allows the strategy
Exceeding contribution limits

Who Should Consider This?

High earners already maxing regular retirement accounts
Those expecting higher future tax rates
People wanting tax diversification in retirement
Individuals with 401(k) plans that support the strategy
Anyone seeking to maximize tax-free retirement savings