Most retirement planning makes a specific kind of mistake: it optimizes one decision at a time. Pick your Social Security age. Calculate your RMD. Run a Roth conversion. Each in isolation, each looking sensible.
The problem is that these four decisions are joined at the hip in real planning. When you claim Social Security changes your taxable income, which changes your IRMAA tier, which changes the cost of your Roth conversions. When you do Roth conversions changes your future RMDs, which changes your future Social Security taxation, which feeds back into the next year’s conversion ceiling. Optimizing them one at a time produces a plan that looks reasonable on each page but loses tens of thousands of dollars in the seams.
This calculator runs all four decisions on shared inputs and surfaces the cross-cutting effects.
The four decisions, all at once
Enter your age, your Traditional IRA balance, your expected Social Security benefit, your current and retirement marginal tax rates, and your filing status. The tool will compute:
- Roth conversion strategy — how much to convert this year, considering your IRMAA ceiling
- Social Security claim age — when to claim, given your tax situation and expected longevity
- RMD trajectory — what your forced withdrawals look like through age 95 under different conversion strategies
- Tax-torpedo and IRMAA exposure — your effective marginal rate at each step
Then it surfaces the interactions:
- If you Roth-convert aggressively in the gap years, your RMDs shrink, your Social Security taxation drops, and your IRMAA tier may improve in your 70s and 80s.
- If you claim Social Security early, your provisional income rises, which lowers your safe conversion ceiling, which forces a slower Roth ladder.
- If you have surviving-spouse status in your projection, the single-filer brackets compress and your future tax rate effectively jumps — a fact most planning software ignores.
Why this matters
Take a hypothetical: a 62-year-old with $1.5M in Traditional IRAs, planning to claim Social Security at 67, expecting a 22% retirement marginal rate.
Run each calculator separately and you get four reasonable answers. Convert $50K/year at 22% — fine. Claim Social Security at 67 — fine. Watch your RMDs grow — fine.
Run them coordinated and a different picture emerges. Maybe the right answer is to convert $80K/year through age 70, delay Social Security to 70, and accept a higher tax bill in the gap years to dramatically reduce the Traditional IRA balance feeding RMDs. The lifetime tax savings can run $80,000–$200,000.
The math works because conversions taken early grow tax-free. Social Security delayed grows by 8% per year of delay. RMDs forced on a smaller balance produce smaller taxable distributions. Each lever helps the others. The seams are where the value is.
What this calculator can’t capture
A word of honesty: a single intake form can’t model your full picture. It doesn’t know about your charitable-giving strategy, your asset location across taxable and tax-deferred accounts, your state tax situation, your healthcare costs, or your beneficiaries’ tax brackets. Real planning factors all of those in.
For households with $500K+ of investable assets, the coordinated multi-year plan is where the meaningful tax savings live. T&T Capital Management does this work for clients as part of fee-only fiduciary tax-coordinated planning. The calculator is a starting point — a clear-eyed view of your base case before the layered optimization begins.
Run yours.