💡 What This Tool Does
The RMD Tax Calculator projects the cumulative federal income tax and Medicare IRMAA surcharges a retiree may pay on Required Minimum Distributions across the full RMD horizon. It models how RMDs interact with Social Security taxation thresholds and Medicare income tiers, so a multi-decade tax burden becomes visible rather than year-by-year.
Questions it answers:
- What is my total projected federal tax exposure from RMDs?
- How many years of IRMAA surcharges will my RMDs likely trigger?
- Does the Social Security 85% taxable cascade kick in once RMDs begin?
- Could pre-RMD Roth conversions materially reduce the cumulative burden?
For the interactive tool, see the RMD Tax Calculator.
🧮 How the Math Works
RMD start age (SECURE 2.0)
- Born 1950 or earlier — RMDs begin at age 72
- Born 1951–1959 — RMDs begin at age 73 (per IRS proposed regulations)
- Born 1960 or later — RMDs begin at age 75
Annual RMD
RMD = prior-year-end traditional balance ÷ IRS Uniform Lifetime Table divisor for the current age. Divisors decrease each year (27.4 at 72, 26.5 at 73, … 2.0 at 120), which is why RMDs can grow even when the balance is flat or modestly declining.
Federal income tax
The RMD plus any taxable Social Security stacks onto ordinary income; the standard deduction is subtracted; the result is run through the published federal marginal brackets. Tax shown is the federal portion only — state income tax varies and is not modeled.
Medicare IRMAA surcharge
IRMAA is a 2-year-lookback income surcharge applied as cliff-style tiers on Medicare Part B and Part D premiums — crossing a threshold by one dollar can move you into the next tier. MAGI in year N sets your premium tier in year N+2. The calculator applies the published 2026 tier thresholds and combined Part B + Part D annual surcharge amounts.
Social Security taxation cascade
Up to 50% of Social Security is taxable when provisional income (AGI plus half of SS benefit) exceeds $25,000 single / $32,000 married; up to 85% is taxable above $34,000 single / $44,000 married. The calculator applies the IRS Pub 915 formula so the marginal cost of an extra RMD dollar reflects the SS cascade where the taxpayer is in the phase-in band.
⚖️ Limitations & Assumptions
- Federal only. State income tax, Net Investment Income Tax (NIIT), and Additional Medicare Tax are not modeled.
- Filing status held constant. The calculator does not model a surviving-spouse filing-status change (MFJ→Single) or its bracket-compression effect. For that comparison, see the full Tax Optimization tool.
- Single account, single owner. Spouse RMDs and inherited account RMDs are not aggregated here.
- 2026 IRS values. Bracket thresholds, standard deduction, IRMAA tiers, and Uniform Lifetime divisors reflect published 2026 values; legislative changes after that date may alter results.
- Educational, not advice. Output is a directional projection for planning conversations, not personalized tax advice.
🔗 Related Tools
- Roth Conversion Analyzer — full multi-year conversion strategy with break-even analysis
- Tax Optimization — scenario-based comparison including IRMAA tier control
- Strategy Comparison — compare side-by-side withdrawal and conversion strategies