Calculators
Medication Adherence Calculator
Calculate medication adherence as proportion of days covered (PDC) and medication possession ratio (MPR) from refill records.
- Runs in your browser
- Nothing uploaded
The tool
Enter your numbers below. Results update as you type, and nothing leaves your browser.
Everything you enter stays on your own machine. Nothing is sent to us or to anyone else, which you can confirm in your browser network tab.
What people use it for
- Pharmacy adherence programmes
- Health plan quality reporting
- Medication therapy management
- Patient counselling
About this tool
What the Medication Adherence Calculator does
Pharmacies and health plans measure adherence from refill data. Proportion of days covered (PDC) counts the days a patient had medication on hand during a period, capped so overlaps are not double-counted; medication possession ratio (MPR) sums days supplied. A PDC of 80% or more is the common adherence threshold.
Formula
- PDC = days with medication on hand ÷ days in period (early refills shift forward)
- MPR = total days supplied ÷ days in period (capped at 100%)
Worked example
Using the starting values in the calculator above:
| Input | Value |
|---|---|
| Measurement period | 180 days |
| Refills | 5 entries |
| Result | Value |
|---|---|
| Proportion of days covered | 83.3% |
| Status | Adherent (PDC 80% or more) |
| Medication possession ratio (capped) | 83.3% |
| Days without medication | 30 |
How to read the result
PDC is preferred by many quality programmes because it does not overstate adherence when patients refill early.
Low adherence is a prompt for a conversation about side effects, cost and routines.
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Questions
Questions about this tool
The things clients actually want to know — costs, timelines, ownership and what happens after launch.
Proportion of days covered: the share of days in a period a patient had medication available.
A PDC of 80% or more is the standard threshold for many chronic medications.
MPR adds up all days supplied, so early refills can push it above true coverage.
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