When Roth Conversions Make the Most Sense
- Early retirement years (60-72) before RMDs begin — often the lowest income years of your retirement life
- Years when your taxable income is unusually low (one-time deduction, low-income year, medical expenses)
- When the 12% or 22% tax bracket has room — the conversion fills it at those rates vs. potentially higher future rates
- When you believe federal tax rates will rise in the future — converting at current rates locks in today’s tax
- When you want to reduce future RMDs on a large Traditional IRA balance
- When you have heirs in higher tax brackets who will inherit a Traditional IRA and face high ordinary income tax
A couple retires at 65 with no pension, $35,000/year in Social Security starting at 70, and $900,000 in Traditional IRA. From 65-70 (before Social Security), their income may be very low — perhaps $20,000/year from part-time work. This window allows $50,000-$75,000 in Roth conversions annually at the 12% bracket, potentially converting $300,000+ before RMDs begin.
How to Calculate Your Optimal Conversion Amount
How to calculate the optimal Roth conversion amount
| Step | Calculation | Example |
|---|---|---|
| 1. Find your current taxable income | All ordinary income for the year | $35,000 from other sources |
| 2. Find top of your target bracket | 12% bracket top for MFJ: ~$94,300 (2025) | $94,300 |
| 3. Calculate available room | Bracket top - Current income | $94,300 - $35,000 = $59,300 room |
| 4. Convert to fill bracket | Transfer this amount from Traditional to Roth | Convert $59,300 |
| 5. Verify no IRMAA cliff crossing | Check MAGI stays below $206,000 (MFJ) | New MAGI: $94,300 — safe |
Conversion Tax Math: Real Example
Convert $50,000 at 22% bracket rate: pay $11,000 in current-year federal tax. That $50,000 grows tax-free in the Roth. If it doubles to $100,000 in 10 years, you saved taxes on $50,000 of growth. Compare: keeping it in Traditional IRA and taking as RMD at 28% rate (if tax rates rise): $100,000 × 28% = $28,000 tax. You saved $17,000 by converting at 22% when it was worth $50,000.
Common Roth Conversion Mistakes
- Converting too much in one year — jumping to 32% or 35% bracket negates the advantage vs. waiting
- Forgetting IRMAA impact — conversion income is counted in MAGI for Medicare premiums 2 years later
- Not paying the conversion tax from outside funds — paying tax from the converted amount reduces the Roth balance
- Converting before using up available tax deductions — take all deductions first to reduce taxable income
- Not accounting for Social Security taxation — conversions add to combined income and may make more SS taxable
- Converting large amounts without modeling multi-year strategy — optimal conversions are a multi-year plan
Calculate Your Roth Conversion Long-Term Value
Model how a Roth conversion today compounds into significantly more tax-free wealth over time.