2026 Medicare IRMAA Method, Formula & Bracket Examples
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This guide makes the arithmetic behind the 2026 Medicare IRMAA Calculator independently reproducible. It owns the formulas, input definitions, complete published tables, cliff boundaries, precision rules and test evidence. The calculator remains the page that performs a personal scenario.
Calculation sequence
The model first selects the filing-status table, then finds the bracket containing the entered MAGI. All amounts below are monthly and per Medicare beneficiary.
- Monthly IRMAA surcharge = Part B IRMAA + Part D IRMAA.
- Annual IRMAA surcharge = monthly IRMAA surcharge × 12.
- Total Part B premium = $202.90 standard Part B premium + Part B IRMAA.
- Optional combined monthly amount = total Part B premium + entered Part D plan premium + Part D IRMAA.
The optional plan premium never changes the bracket or the IRMAA surcharge.
Inputs and tax-year evidence
Use the filing status and tax year shown on the SSA initial-determination notice. For most 2026 determinations, SSA uses 2024 federal tax-return information; SSA may use 2023 information if 2024 data is unavailable. For IRMAA, MAGI is adjusted gross income plus tax-exempt interest. The special married-filing-separately table applies only when the person lived with a spouse at some point during the tax year.
Complete 2026 adjustment tables
Part D IRMAA is paid in addition to the selected plan premium. The combined column is Part B IRMAA plus Part D IRMAA.
| Bracket | Individual MAGI | Joint MAGI | Part B total | Part B IRMAA | Part D IRMAA | Combined IRMAA |
|---|---|---|---|---|---|---|
| 0 | $109,000 or less | $218,000 or less | $202.90 | $0.00 | $0.00 | $0.00 |
| 1 | Over $109,000 through $137,000 | Over $218,000 through $274,000 | $284.10 | $81.20 | $14.50 | $95.70 |
| 2 | Over $137,000 through $171,000 | Over $274,000 through $342,000 | $405.80 | $202.90 | $37.50 | $240.40 |
| 3 | Over $171,000 through $205,000 | Over $342,000 through $410,000 | $527.50 | $324.60 | $60.40 | $385.00 |
| 4 | Over $205,000 and under $500,000 | Over $410,000 and under $750,000 | $649.20 | $446.30 | $83.30 | $529.60 |
| 5 | $500,000 or more | $750,000 or more | $689.90 | $487.00 | $91.00 | $578.00 |
| MAGI | Part B total | Part B IRMAA | Part D IRMAA | Combined IRMAA |
|---|---|---|---|---|
| $109,000 or less | $202.90 | $0.00 | $0.00 | $0.00 |
| Over $109,000 and under $391,000 | $649.20 | $446.30 | $83.30 | $529.60 |
| $391,000 or more | $689.90 | $487.00 | $91.00 | $578.00 |
Worked example: single filer with $120,000 MAGI
$120,000 is over $109,000 but not over $137,000, so it falls in bracket 1. Part B IRMAA is $81.20 and Part D IRMAA is $14.50. Monthly IRMAA is therefore $95.70, and annual IRMAA is $1,148.40. Total Part B is $284.10. If the person separately enters a $40 Part D plan premium, the optional combined monthly amount is $338.60.
How exact boundaries behave
The published brackets are cliffs, not gradual phase-ins. For a single filer, $109,000 produces no IRMAA while $109,000.01 enters bracket 1. $499,999.99 remains in bracket 4, while $500,000 starts bracket 5. For a joint return, $750,000 starts bracket 5. Under the special married-filing-separately table, $109,000.01 enters bracket 4 and $391,000 starts bracket 5.
Precision, rounding and test record
The calculation uses the entered dollar value without interpolation. Internal formulas retain floating-point precision; displayed money rounds to two decimals. The release includes 25 embedded definition fixtures, 30 independent Medicare scenarios covering exact thresholds and values one cent above them, and the full CalculatorGeek definition suite. Invalid, negative and non-finite inputs are rejected by the definition validation layer.
Scope and limitations
Calendar year 2026 only and calculated per beneficiary. It does not determine MAGI, filing status, eligibility, hold-harmless treatment, late-enrollment penalties, Part A IRMAA, the immunosuppressive-drug-only Part B table, plan eligibility, an appeal outcome, or future-year amounts. The married-filing-separately option is limited to the SSA table for people who lived with a spouse during the tax year.
This method reproduces published tables. It is not an SSA determination, tax-return calculation, benefit eligibility decision, appeal service or insurance recommendation. Use the IRMAA notice and evidence guide when the issue is the data on a notice or a later income reduction.
Sources and review status
- CMS — 2026 Medicare Parts A & B Premiums and Deductibles
- SSA — 2026 Medicare premiums and income-related adjustments
- SSA POMS — Modified adjusted gross income for IRMAA
- SSA POMS — 2026 IRMAA sliding-scale tables
- SSA — Medicare Income-Related Monthly Adjustment Amount Life-Changing Event (SSA-44)
Sources and model boundaries checked 2026-10-08. CalculatorGeek Editorial Team reviewed and approved this page on 2026-10-08. Published-table reproduction and documented limitations were retained because the cited authority controls individual determinations.
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