This independent threshold tool does not recalculate Social Security taxability. When Social Security modeling is enabled, use the main calculator ledgers for IRMAA including newly taxable benefits.

Sandbox Concept

Tax-Bracket / IRMAA Cliff Map

See how either a planned Roth conversion or projected IRA distributions can move MAGI through higher federal brackets and Medicare premium surcharge thresholds.

Scenario Inputs

IRMAA Income Test

Filing Status Baseline MAGI Tax-Exempt Interest Included in MAGI Planned Roth Conversion Include Projected IRA Income

IRA Income Age Age 65

Age 65Age 90

Projected Gross IRA Distribution

Open this consideration from the main calculator to load IRA ledger income.

State Tax Rate (%) Tax Bracket / IRMAA Inflation (%)

Linked IRA income comes directly from the no-conversion IRA ledger. Selecting it temporarily disables the Roth conversion so the page shows Baseline MAGI plus only the selected retirement distribution.

--Total Tax + IRMAA Increase

--Blended Cost Rate

--Room Before Next Threshold

--Medicare Premium Increase

Visual Map

Every Additional MAGI Dollar By Marginal Cost

$0 to $300k projected MAGI

Lower bracket Higher bracket IRMAA cliff High marginal cost Selected projected MAGI

Cost Curve

Cumulative Tax + IRMAA Cost

Through selected projected MAGI

Cliff Detail

Thresholds Crossed By Selected Income

Cliff	Added MAGI Where It Hits	Marginal Cost After Cliff	Why It Matters

Next Watch Points

Upcoming Thresholds If Added Income Increases

Cliff	Additional Room	Added MAGI Where It Hits	Why It Matters

2026 Medicare Premium Detail

What Each IRMAA Tier Costs

Tier	MAGI Range	Part B / Month	Part D IRMAA / Month	Combined / Month	Increase From Prior Tier / Month	Annual Increase From Prior Tier

Sources: 2026 Medicare Costs, CMS 2026 Part B and Part D schedules, and the planning discussion in Northern Trust’s “Avoiding the IRMAA Cliffs.”