Medicare Part D Cost Calculator
Medicare Part D has three costs that stack up over a year: the monthly premium you pay whether or not you fill a prescription, the deductible you pay first, and then your share of each drug’s price until you reach the annual out-of-pocket cap. This calculator adds those three layers together for 2026, using your own premium, deductible, and total drug costs, so you can see your full-year number instead of guessing from a monthly figure.
Estimate only, for covered drugs under the standard 2026 benefit design. Your plan’s copays, tier rules, and Extra Help status can change the result.
Quick Answer
In 2026, your Part D cost is your annual premiums plus your drug out-of-pocket, which is capped at $2,100 for covered drugs. With a $40 monthly premium, a $615 deductible, and $3,000 in prescriptions, you would pay $1,691.25 for the year: $480 in premiums, $615 of deductible, and $596.25 in 25% coinsurance. The old coverage gap, often called the donut hole, no longer exists.
How Part D costs work in 2026
Part D follows a short sequence. First you pay your monthly premium, every month, whether or not you fill a prescription. Then, at the pharmacy, you pay the full price of covered drugs until you have paid your plan’s deductible. After that, the standard benefit charges 25% coinsurance, meaning you pay a quarter of each covered drug’s price and the plan pays the rest. Once your own spending on covered drugs, deductible plus coinsurance, reaches $2,100, you pay $0 for covered drugs for the rest of the calendar year. Your premium keeps running after the cap, because premiums never count toward it.
That last point is the one most quick estimates get wrong. A tool that folds premiums into the cap, or stops charging premiums after $2,100, understates the year by up to several hundred dollars. This calculator keeps the two buckets separate: premiums in one line, capped drug spending in the other, and the total is simply their sum.
2026 Part D figures at a glance
The figures below are the 2026 standard-benefit numbers published by the Centers for Medicare and Medicaid Services (CMS). Your plan may charge less than the maximum deductible, and your premium is set by your plan, not by CMS, so treat the national base premium as a reference point, not as your price.
| Figure | 2026 amount | What it means |
|---|---|---|
| National base beneficiary premium | $38.99 per month | Reference premium used for penalties and subsidies; actual plan premiums vary |
| Maximum annual deductible | $615 | Most you can be asked to pay before coverage starts; many plans charge less |
| Standard coinsurance | 25% | Your share of covered drug costs after the deductible, under the standard design |
| Annual out-of-pocket cap | $2,100 | After this, $0 for covered drugs for the rest of the year; premiums excluded |
| Insulin, one month’s supply | $35 maximum | Per covered insulin product, in every phase, with no deductible applied |
| Recommended adult vaccines | $0 | ACIP-recommended adult vaccines under Part D carry no cost sharing |
Two related costs sit outside this calculator on purpose. Part B, which covers doctor visits and outpatient care, has its own $202.90 standard monthly premium and $283 annual deductible for 2026, and it is not part of a Part D total. If you are comparing your whole Medicare bill, run the health costs separately rather than adding Part B into a Part D figure: our health insurance cost per month calculator is the place to model a monthly health budget, while this page stays strictly on prescription drugs.
The formula, step by step
Annual premiums equal monthly premium times 12. Deductible paid equals the smaller of your total drug costs and your plan’s deductible. Coinsurance equals 25% of whatever drug costs remain after the deductible. Drug out-of-pocket equals deductible paid plus coinsurance, capped at $2,100. Total annual cost equals annual premiums plus capped drug out-of-pocket.
Worked example, using the pre-filled inputs: $40 times 12 is $480 in premiums. Drug costs of $3,000 exceed the $615 deductible, so deductible paid is $615. The remaining $2,385 at 25% is $596.25 in coinsurance. Drug out-of-pocket is $615 plus $596.25, or $1,211.25, which is below the cap, so no capping applies. The total is $480 plus $1,211.25, or $1,691.25.
A high-cost example shows the cap doing its work. With the same $40 premium and $615 deductible but $10,000 in drug costs, coinsurance would be 25% of $9,385, or $2,346.25, and uncapped drug spending would reach $2,961.25. The cap cuts that to $2,100, so the total is $480 plus $2,100, or $2,580. Without the cap, the same person would have paid $3,441.25, so the cap is worth $861.25 in that year.
What other calculators get wrong
Three mistakes show up again and again. The first is the zombie donut hole: tools built before 2025 still ask for a coverage limit and charge a higher share in a gap phase that no longer exists. Since 2025 the Inflation Reduction Act replaced the gap with the hard cap, so any calculator still modelling a gap phase is modelling a benefit that ended. The second is counting premiums toward the cap, which makes high-cost years look cheaper than they are. The third is presenting a flat 25% as if every drug worked that way: many plans charge flat copays by tier instead, and insulin is capped at $35 per month regardless of phase. This calculator is honest about that limit: it models the standard 25% design, and if your plan uses tier copays, your real number will differ, usually by less than the gap-phase error but still worth checking against your plan’s formulary.
Other gaps are about what the tool leaves out rather than what it miscalculates. Most Part D tools ignore Extra Help, the low-income subsidy that can cut premiums, deductibles, and copays sharply, and they ignore the Medicare Prescription Payment Plan, which spreads your out-of-pocket costs across monthly bills without reducing the total. If you qualify for Extra Help, this calculator will overstate your cost: check the premium assistance calculator for how assistance changes a monthly premium, and ask your plan or your State Health Insurance Assistance Program (SHIP) for a plan-specific figure before enrolling. For retirement budgeting as a whole, the Social Security early retirement calculator puts Medicare costs in the wider context of income timing, which is where a Part D premium actually bites.
When the estimate will differ from your bill
Your bill can differ for legitimate reasons, and knowing them in advance stops a nasty surprise. If some of your drugs are on a tier your plan exempts from the deductible, you will pay less deductible than this calculator shows. If your plan charges a flat $10 or $45 copay instead of 25% coinsurance, expensive brand drugs will cost you less and cheap generics may cost you slightly more than modelled. Non-covered drugs never count toward the cap at all, so a drug your plan does not cover is paid in full on top of this total. And if your income is above the IRMAA thresholds, your Part D premium carries an income-related surcharge that this calculator does not add, because it needs your tax return, not just your plan card, to compute it. None of these make the tool wrong; they mark the boundary between a standard-design estimate and a plan-specific quote, and the plan-specific quote always wins.
A practical way to use the result: run it once with your current drug list at today’s prices, once with the list your doctor expects next year, and once with the cap case, meaning drug costs high enough to hit $2,100. Those three numbers bound your year. If the cap case is only a little above your base case, the cap is doing most of your budgeting for you, and plan choice matters less than it looks. If the three numbers are far apart, the deductible and the tier structure matter a lot, and comparing two plans drug by drug is worth an afternoon.
Frequently asked questions
The cap is $2,100 for covered Part D drugs in 2026. It covers your deductible plus your coinsurance and copays on covered drugs. Once you reach it, you pay $0 for covered drugs for the rest of the year, but your monthly premium continues.
No. The coverage gap known as the donut hole was closed in 2025 and replaced by the $2,100 annual out-of-pocket cap. Calculators that still ask for a coverage limit are using the pre-2025 benefit design.
No. Only what you pay for covered drugs counts: your deductible, coinsurance, and copays. Premiums are paid on top of the cap, so your total year can reach $2,100 in drug costs plus a full year of premiums.
The maximum is $615. Many plans charge less, and some charge $0. Enter your own plan’s deductible in the calculator, not the maximum, if you know it.
Each covered insulin product costs at most $35 for a one-month supply, in every coverage phase, with no deductible applied. This calculator’s 25% model does not apply to insulin, so insulin users should expect a lower drug total than the standard model shows.
It is a voluntary option that spreads your Part D out-of-pocket costs across monthly bills during the year. It does not reduce your total cost, it only changes when you pay it. Ask your plan to enroll you if large pharmacy bills early in the year are the problem.
Yes, sharply. Extra Help, the Part D low-income subsidy, can reduce or remove your premium and deductible and cap your copays at a few dollars. If you qualify, this calculator overstates your cost and a plan-specific Extra Help figure should be used instead.
Most often because your plan uses flat tier copays instead of 25% coinsurance, exempts some drugs from the deductible, or does not cover a drug at all. Non-covered drugs never count toward the cap. An IRMAA surcharge on your premium, if your income is above the threshold, also sits outside this estimate.
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References
- Medicare.gov, Costs for Medicare drug coverage: deductible, coinsurance, and the out-of-pocket cap explained.
- KFF, Medicare Part D in 2026: plan availability, average premiums, and benefit design context.