How Is Medicare Cost Calculated? (2026)

Direct Answer

It depends on four things: which Medicare parts you have, your income from two years prior, when you first enrolled, and whether you carry supplemental coverage. In 2026, Original Medicare charges a $202.90 monthly Part B premium and a $283 annual deductible, with no cap on your share of costs. Add Medicare Advantage, Medigap, or Part D, and the formula changes again for each program.

The Four Inputs That Set Your Medicare Cost

Medicare cost is not one number; it is a formula with four inputs. First, which parts you are enrolled in: Part A (hospital), Part B (medical), Part C (Medicare Advantage), and Part D (drugs) each have their own premium and deductible schedule. Second, your Modified Adjusted Gross Income (MAGI) from two years earlier determines whether you pay a base premium or a higher, income-adjusted one through IRMAA. Third, when you enrolled matters: signing up for Part B or Part D late without qualifying coverage triggers a permanent monthly penalty added to your premium for as long as you are enrolled. Fourth, whether you layer on Medicare Advantage, Medigap, or a standalone Part D plan changes your deductible, coinsurance, and out-of-pocket exposure entirely.

How Original Medicare Costs Are Calculated in 2026

Original Medicare splits its calculation between Part A and Part B. About 99% of beneficiaries pay $0 for Part A because they or a spouse worked at least 40 quarters (10 years) paying Medicare payroll taxes. Those with 30 to 39 quarters pay a reduced Part A premium of $311 a month in 2026, and those with fewer than 30 quarters pay the full $565 a month. Once Part A applies, the inpatient hospital deductible is $1,736 per benefit period in 2026, followed by daily coinsurance of $434 for days 61 to 90, $868 per lifetime reserve day, and $217 a day for skilled nursing facility days 21 to 100.

Part B follows a separate calculation: the standard monthly premium is $202.90 in 2026, the annual deductible is $283, and after the deductible is met, Medicare pays 80% of the Medicare-approved amount for most services while you pay the remaining 20% coinsurance indefinitely, with no yearly out-of-pocket maximum. That uncapped 20% is the single biggest reason people add Medigap or switch to Medicare Advantage.

How IRMAA Raises Your Calculated Cost Based on Income

IRMAA (Income-Related Monthly Adjustment Amount) is the surcharge the Social Security Administration adds to Part B and Part D premiums for higher earners, using tax returns from two years earlier. For 2026 premiums, the Social Security Administration looks at your 2024 MAGI. Individuals filing single with 2024 MAGI above $109,000, or couples filing jointly above $218,000, move into an IRMAA bracket. The Part B surcharge for 2026 ranges from $81.20 to $487.00 a month on top of the $202.90 standard premium, making the total Part B premium anywhere from $284.10 to $689.90 depending on the bracket. A separate Part D surcharge of $14.50 to $91.00 a month is added directly to your drug plan premium.

CMS estimates about 8% of Medicare beneficiaries pay an IRMAA surcharge in 2026. If your income dropped since 2024 because of retirement, divorce, or another life-changing event, you can file Form SSA-44 to ask Social Security to recalculate your IRMAA using more recent income instead of the two-year-old tax return.

How Medicare Advantage Recalculates the Cost

Medicare Advantage (Part C) replaces the uncapped Original Medicare formula with a plan-specific one that still requires you to keep paying your Part B premium. The average Medicare Advantage premium is $11.02 a month in 2026, and many plans charge $0. Instead of a flat 20% coinsurance forever, each plan sets its own copays and coinsurance for specific services, and by law every plan must cap total in-network out-of-pocket spending at $9,250 in 2026 (or $13,900 combined in-network and out-of-network). The enrollment-weighted average cap that plans actually set is lower, around $5,421, with HMOs averaging $4,636 and PPOs averaging $6,592.

How Medigap and Part D Change the Math

Medigap does not replace Original Medicare's formula; it pays some or all of what that formula leaves you owing. A Medigap Plan G policy for a 65-year-old typically costs $110 to $200 a month in 2026 depending on state and underwriting, and in exchange it covers the Part A deductible, Part A coinsurance, and most of the Part B coinsurance that would otherwise be uncapped. You still pay the $283 Part B deductible yourself under Plan G, then Medigap picks up nearly everything else.

Part D drug plans run on a separate formula entirely. The national base beneficiary premium is $38.99 a month in 2026, though actual plan premiums vary widely above and below that figure. Under the redesigned Part D benefit, you pay a deductible of up to $615, then roughly 25% coinsurance on covered drugs, until your true out-of-pocket spending hits $2,100 in 2026, after which the plan covers 100% of costs for the rest of the year. Insulin is capped separately at $35 a month regardless of which phase you are in.

Alternatives If the Calculated Cost Is Too High

Four programs can lower or eliminate the standard Medicare cost calculation for people with limited income and assets. Medicare Savings Programs (QMB, SLMB, and QI), run through each state's Medicaid agency, pay the Part B premium and, for QMB, also the Part A and Part B deductibles and coinsurance. Extra Help (the Part D Low-Income Subsidy) reduces or eliminates your Part D premium, deductible, and copays; see Extra Help eligibility for income limits by household size. About 12 million Americans qualify for both Medicare and Medicaid as dual-eligibles, in which case Medicaid picks up nearly all remaining cost-sharing. If your income is too high for those programs but you still want predictable costs, comparing Medicare Advantage and Medigap directly, as in Medigap vs Medicare Advantage, is the next step.

To act on any of this, use the Medicare Plan Finder at medicare.gov to compare exact 2026 premiums and out-of-pocket caps by zip code, or call your State Health Insurance Assistance Program (SHIP) for free one-on-one help. The Annual Enrollment Period runs October 15 through December 7, 2026 for coverage starting January 1, 2027, and the Medicare Advantage Open Enrollment Period runs January 1 through March 31, 2026 for one plan switch.

How is my Medicare Part B premium calculated in 2026?

The standard Part B premium is set by CMS each year using a formula tied to projected Medicare Part B spending and is $202.90 a month in 2026. If your 2024 income was above $109,000 (single) or $218,000 (joint), an IRMAA surcharge is added on top, raising the total to as much as $689.90 a month.

What is IRMAA and how does it raise my Medicare cost?

IRMAA (Income-Related Monthly Adjustment Amount) is a surcharge added to Part B and Part D premiums for higher earners, based on your tax return from two years earlier. For 2026, it applies if your 2024 MAGI exceeded $109,000 single or $218,000 joint, adding $81.20 to $487.00 a month to Part B and $14.50 to $91.00 to Part D.

Does Medicare Advantage cost less than Original Medicare in 2026?

Often, yes, on the premium side: the average Medicare Advantage premium is $11.02 a month in 2026 versus the $202.90 Part B premium you pay either way. But Medicare Advantage shifts cost into plan-specific copays and coinsurance, capped at $9,250 in-network, so your total cost depends heavily on how much care you use.

What happens if I don't buy supplemental coverage?

Original Medicare's Part B coinsurance is 20% with no annual out-of-pocket maximum, so a serious illness or hospitalization can generate thousands of dollars in cost-sharing. Without Medigap or Medicare Advantage's built-in out-of-pocket cap, you carry that uncapped 20% coinsurance yourself for every covered service.

How much does Medigap cost in 2026?

A Medigap Plan G policy for a 65-year-old typically runs $110 to $200 a month in 2026, varying by state, gender, and underwriting class. In exchange, it covers most of the Part A and Part B cost-sharing that Original Medicare's formula leaves uncapped, aside from the $283 Part B deductible.

What is the Medicare Part D out-of-pocket cap in 2026?

The Part D true out-of-pocket cap is $2,100 in 2026, up from $2,000 in 2025. After you and your plan combine to spend that amount on covered drugs, your plan pays 100% of costs for the remainder of the calendar year. Insulin is separately capped at $35 a month.

Can I get help paying my Medicare costs if I have low income?

Yes. Medicare Savings Programs run through your state Medicaid agency can pay your Part B premium and, in some cases, your deductibles and coinsurance. Extra Help lowers Part D premiums and copays. About 12 million dual-eligible Americans qualify for both Medicare and Medicaid, which covers nearly all remaining cost-sharing.

What's the difference between Medicare Advantage and Medigap costs?

Medicare Advantage bundles Part A, Part B, and usually Part D into one plan with a low or $0 premium but variable copays capped at $9,250 in-network in 2026. Medigap keeps you on Original Medicare, adds a separate premium of $110 to $200 a month for Plan G, and covers most remaining coinsurance instead of capping it.