Medicare Part B Premium Calculator (2026 IRMAA Brackets)

Medicare Part B has a standard premium that everyone in the bottom income bracket pays, and an income-related monthly adjustment amount (IRMAA) layered on top for everyone above it. For 2026 the standard Part B premium is $202.90 a month, and the first single-filer threshold is $109,000 of modified adjusted gross income.

Two features of the design cause almost all the surprise. The first is that IRMAA is a cliff, not a taper. Each bracket's surcharge applies in full to the first dollar above its threshold. There is no phase-in across a bracket, so a single dollar of MAGI can cost the entire annual step, and twice that for a married couple, because the surcharge is billed to each enrolled spouse individually off the same joint MAGI.

The second is the two-year lag. Your premium for a given year is set from the MAGI on the tax return filed two years earlier. Your 2026 premium comes from your 2024 return. That is why a newly retired person so often pays a surcharge priced off their last full year of work, the highest-income year of their life, billed to them after the income has stopped.

This calculator prices both effects: where you sit today, how far you are from the next cliff, and what a specific slice of extra income -- a Roth conversion, a capital gain, a property sale -- would actually cost you in premiums.

The premium is a step function of MAGI, and the marginal cost of extra income is a difference of two evaluations of that function:

Step 1 -- Locate the bracket. The 2026 single ceilings are $109,000, $137,000, $171,000, $205,000 and $500,000, with a sixth bracket above. $108,000 falls in the first. Tier 1 of 6

Step 2 -- Look up the Part B surcharge for that bracket. $0.00 a month

Step 3 -- Add it to the standard premium. This is the headline. $202.90 + $0.00 = $202.90 a month

Step 4 -- Look up the Part D surcharge for the same bracket. The thresholds are identical for both parts, so a household that crosses one crosses both. $0.00 a month

Step 5 -- Total the monthly cost for one enrollee. $202.90 + $0.00 = $202.90

Step 6 -- Annualise it for the household. $202.90 x 12 x 1 enrollee = $2,434.80 a year

Step 7 -- Measure the headroom before the next cliff. The bracket ends at $109,000, so the headroom is the dollars that would still keep you inside it. $109,000 - $108,000 + $1 = $1,001

Step 8 -- Price the cost of crossing. The tier 2 surcharges are $81.20 for Part B and $14.50 for Part D. ($81.20 - $0.00) x 12 = $974.40 of Part B ($14.50 - $0.00) x 12 = $174.00 of Part D $974.40 + $174.00 = $1,148.40 a year for the household

Step 9 -- Re-evaluate the whole premium with the extra income added. $108,000 + $1,500 = $109,500 of MAGI, which lands in tier 2 ($202.90 + $81.20 + $14.50) x 12 = $3,583.20 a year

Step 10 -- Difference the two household annual figures. $3,583.20 - $2,434.80 = $1,148.40 of added annual cost

Step 11 -- Express that as a rate on the extra income. $1,148.40 / $1,500 = 76.56%

That last figure is the whole point of the page. The marginal cost of a dollar of MAGI is exactly zero everywhere inside a bracket and enormous at the single dollar that crosses one.

A single retiree filed a 2024 return showing $108,000 of MAGI. In 2026 she is enrolled in Medicare and is considering realising $1,500 of capital gains in the look-back year.

Step 1 -- Where she sits. Tier 1, paying the standard $202.90 a month with no surcharge.

Step 2 -- Her annual cost. $202.90 x 12 = $2,434.80.

Step 3 -- How close she is to the edge. The first threshold is $109,000. She has $1,001 of headroom.

Step 4 -- What the extra $1,500 does. It takes her to $109,500, past the threshold, into tier 2.

Step 5 -- Her new annual cost. $298.60 a month across Part B and the Part D surcharge, or $3,583.20 a year.

Step 6 -- What the $1,500 cost her. $1,148.40, which is 76.56% of the gain.

Step 7 -- What $999 would have cost her. Nothing at all.

Change one input and the asymmetry sharpens further. A married couple at $217,000 joint MAGI with both spouses enrolled faces the same $1,500 crossing the first joint threshold of $218,000 -- but the surcharge is billed to each spouse separately off the same joint return, so the crossing costs twice as much. Joint thresholds are double the single ones; joint costs are double too, which means the joint brackets are not more generous per person at all.

• Your Part D plan premium. Only the Part D IRMAA surcharge is priced. The premium for the drug plan itself is set by the insurer and varies widely.
• The Part B deductible, coinsurance, and any Medigap or Medicare Advantage premium. None of these are income-related and none are modelled.
• The hold-harmless provision, which limits Part B premium increases for some beneficiaries whose premiums are deducted from a Social Security benefit.
• Late enrolment penalties for Part B or Part D, which are permanent additions unrelated to income.
• What actually counts in MAGI. The calculator takes the figure you enter. The MAGI used for IRMAA includes tax-exempt interest, which catches many people out.
• Any appeal. A drop in income does not change the premium on its own. See the IRMAA appeal calculator for the eight life-changing events that allow SSA to use a more recent year.

• Entering this year's income. The premium is set from the return filed two years earlier. For 2026 premiums, enter your 2024 MAGI.
• Forgetting tax-exempt interest. Municipal bond interest is added back for IRMAA purposes even though it is not taxable income. A portfolio built for tax-free income can still trigger a surcharge.
• Assuming the surcharge phases in. It does not. There is no gradual increase across a bracket, which means the last dollar before a threshold is free and the first dollar after it costs the whole step.
• Assuming a couple's thresholds are more generous. They are exactly double the single thresholds, and the surcharge is billed twice, once to each enrolled spouse. Per person, they are identical.
• Timing a Roth conversion without checking the cliff. A conversion that makes excellent income tax sense can cost more than it saves once the Medicare surcharge two years later is counted.
• Ignoring the one-year-only nature of the damage. A one-off income spike raises the premium for one year, then the surcharge falls away once the tax data catches up. That is often worth accepting, but it should be a decision rather than a surprise.

• Centers for Medicare and Medicaid Services, 2026 Medicare Parts A and B premiums and deductibles fact sheet -- the $202.90 standard Part B premium and the six-tier IRMAA schedule with its Part B and Part D surcharges, carried in engine/tables/2026/irmaa.json. https://www.cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-deductibles
• Social Security Administration POMS HI 01120.005, Life Changing Events -- the exclusive list of events for which SSA will use a more recent tax year. https://secure.ssa.gov/poms.nsf/lnx/0601120005