Guide
Roth conversion planning
Last updated: May 2026
A Roth conversion can lower future tax drag in retirement, but conversions are paid from current taxable income and create real tradeoffs in the years around retirement.
This guide treats conversions as an educational scenario design process, not a universal strategy. Use it to compare conversion windows and understand risk, not as direct recommendation.
Practical retirement planning workflow
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01. Define a five-year retirement gap window.
Conversions often fit well where income is lower and before regular Social Security starts.
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02. Estimate household tax bracket under base retirement spending.
Use a practical income baseline that includes withdrawals and bridge costs.
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03. Test three conversion sizes for each year.
Use partial conversions to see where tax cost and future flexibility meet.
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04. Track tax payment source.
Use outside cash or separate liquidity before assuming portfolio taxes are always affordable.
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05. Check side effects around Medicare-related subsidies.
Higher income can increase Medicare premiums for some households; include this in planning notes.
Worked example: first five years after retirement
Assume $320,000 in pre-tax and $80,000 in Roth at retirement. The household sets retirement spending at $58,000 and delays Social Security to age 67. They test three conversion options from the pre-tax account in year one.
| Year-one conversion amount | Tax cost example | Immediate impact | Use-case warning |
|---|---|---|---|
| $0 | Lowest | More pre-tax balance preserved | May miss growth compounding benefit in Roth |
| $30,000 | Moderate | Balanced growth and taxable income | Watch for Medicare premium jumps and RMD timing |
| $60,000 | Higher | Lower future tax drag potential | Requires robust cash for taxes and may reduce flexibility |
None of these is automatically better. The right amount depends on your tax assumptions and whether the conversion period stays stable under plan stress tests.
Checklist
- Record tax cost for each conversion year, not only annual total.
- Verify cash available to pay conversion taxes without forced early withdrawals.
- Track any interaction with healthcare and premium assumptions.
- Model RMD-trigger year separately.
- Document why you selected each conversion amount.
Common mistakes
- Converting all at once without scenario comparison.
- Not preparing non-investment cash for taxes.
- Ignoring Medicare premium interactions.
- Over-converting because of a single return outlook.
Monte Carlo interpretation
Conversion decisions are tax-driven and should remain coordinated with success-rate sensitivity, not success-rate value alone.
FAQ
Is conversion always best before age 67?
Not always. It depends on income timing, required cash, and household health assumptions.
Can this calculator choose my conversion amount?
No. Use it to compare retirement outcomes across retirement timing and spending assumptions.
Is there a guaranteed tax benefit?
No. Outcomes depend on your assumptions and tax law context.
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