Mega Backdoor Roth Calculator
Calculate after-tax 401(k) contributions converted to Roth. Understand 401(k) limits, in-plan Roth conversions, and the tax benefits of contributing beyond standard pre-tax limits.
401(k) Details
2024 401(k) Contribution Limits
Employee Pre-Tax/Roth Limit:$23,000
Catch-Up (Age 50+):$7,500
Total Plan Limit:$69,000
Total with Catch-Up:$76,500
After-tax contributions allowed after pre-tax/Roth contributions up to total plan limit ($69K). Employer match included in total.
Your After-Tax Room
Salary:$150000
Employer Match:$9000.00
Pre-Tax/Roth Limit:$23000
After-Tax Room:$37000.00
Your Contribution:$30000.00
Conversion Type:In-Plan Roth
Roth Balance After 10 Years
$443507.98
Total Contributions:$300000.00
Tax-Free Growth:$143507.98
Annual Conversion Schedule
| Year | After-Tax Contrib | Conversion Type | Tax on Growth | Roth Balance |
|---|---|---|---|---|
| 2026 | $30000 | In-Plan Roth | $0 | $32100 |
| 2027 | $30000 | In-Plan Roth | $0 | $66447 |
| 2028 | $30000 | In-Plan Roth | $0 | $103198 |
| 2029 | $30000 | In-Plan Roth | $0 | $142522 |
| 2030 | $30000 | In-Plan Roth | $0 | $184599 |
| 2031 | $30000 | In-Plan Roth | $0 | $229621 |
| 2032 | $30000 | In-Plan Roth | $0 | $277794 |
| 2033 | $30000 | In-Plan Roth | $0 | $329340 |
| 2034 | $30000 | In-Plan Roth | $0 | $384493 |
| 2035 | $30000 | In-Plan Roth | $0 | $443508 |
Mega Backdoor Roth Explained
- What: Contribute after-tax dollars to 401(k) beyond $23K pre-tax/Roth limit. Convert to Roth immediately. Growth tax-free.
- How: 1) Max out $23K pre-tax/Roth 401(k), 2) Contribute after-tax up to total limit ($69K), 3) Convert to Roth (in-plan or roll to IRA).
- In-Plan Roth: Best option. Convert after-tax to Roth within 401(k). No taxable growth before conversion. All growth tax-free.
- Roll to IRA: If plan doesn't offer in-plan Roth. Roll after-tax to Roth IRA. Growth before roll is taxable.
- Benefits: Contribute up to $69K total, growth tax-free in Roth, no income limits, no RMDs (Roth 401(k) or Roth IRA).
- Requirements: Plan must allow after-tax contributions. Plan must allow in-plan Roth OR allow rollovers while employed.
In-Plan Roth vs Roth IRA Roll
In-Plan Roth Conversion
- Best: immediate conversion
- No tax on growth before conversion
- Stay in 401(k) plan
- Subject to plan investment options
- May have limited withdrawals
- No 5-year rule per conversion
Roll to Roth IRA
- Growth taxed before roll
- More investment freedom
- Easier withdrawals
- No RMDs ever
- 5-year rule applies
- Plan must allow in-service rollover
Mega Backdoor Roth Benefits
- Supercharge Roth: Contribute $23K + after-tax up to $69K. More Roth savings than IRA limit ($7K) alone.
- No Income Limits: High earners can do mega backdoor Roth. No Roth IRA income limits apply.
- Tax-Free Growth: All growth in Roth is tax-free forever. No tax on withdrawals.
- No RMDs: Roth 401(k) no RMDs (SECURE 2.0). Roth IRA no RMDs ever. More flexibility in retirement.
- Estate Benefit: Roth better for heirs. Tax-free inheritance. Heirs get same tax benefits.
- Early Access: Roth contributions (not conversions) accessible anytime tax-free. Conversions: 5-year rule.
- Employer Match: Employer match on after-tax contributions if plan allows. More employer money!
Mega Backdoor Roth Limitations
- Plan Must Allow: Not all plans allow after-tax contributions. Not all allow in-plan Roth or in-service rollovers. Check with HR.
- Admin Complexity: Manual conversions sometimes required. Missed conversions = growth taxed. Auto-convert best.
- Withdrawal Rules: In-plan Roth may have withdrawal restrictions. Need to roll to IRA for full access.
- 5-Year Rule: Roth IRA conversions have 5-year rule. In-plan Roth: no per-conversion 5-year rule, but overall 5-year rule may apply.
- Growth Tax (Roll): Rolling to Roth IRA: growth before conversion taxed. In-plan Roth preferred to avoid.
- Employer Match: Some plans do NOT match after-tax. Check plan documents. Match may only apply to pre-tax/Roth.
How to Set Up Mega Backdoor Roth
- Step 1: Check if plan allows after-tax contributions. Ask HR or read plan documents.
- Step 2: Check if plan allows in-plan Roth conversions OR in-service rollovers to IRA.
- Step 3: Max out $23K pre-tax/Roth contributions first. After-tax only after pre-tax/Roth maxed.
- Step 4: Set up after-tax contributions. Calculate room: $69K total - $23K - employer match = after-tax room.
- Step 5: Convert immediately (in-plan) OR roll to Roth IRA frequently. Minimize growth before conversion.
- Step 6: Automate if possible. Auto-convert after-tax to Roth eliminates manual conversion timing risk.
Common Questions
- Can I do backdoor Roth IRA + mega backdoor? Yes! $7K IRA conversion + $46K after-tax 401(k). Both can be done same year.
- Does employer match count toward after-tax? Employer match part of $69K total limit. Reduces after-tax room.
- What if plan does not allow after-tax? Cannot do mega backdoor Roth. Use regular backdoor Roth IRA ($7K) instead.
- Auto-convert vs manual? Auto-convert best - immediate conversion, no growth tax. Manual: risk of missing conversion timing.
- Can I withdraw mega backdoor Roth? In-plan Roth: follow plan withdrawal rules. Roth IRA: contributions anytime, conversions 5-year rule.