Migraine days calculator
A neurologist reads a migraine diary by three numbers a month — headache days, migraine days, medication days — because the definitions of chronic migraine and medication-overuse headache are written in exactly those units. Put your months in and see where each one sits against those lines. This won’t tell you what you have: the lines are orientation, the reading is a clinician’s, and a part-month is never scaled up into a monthly figure.
Why three numbers, and why months
Memory is a bad instrument for headaches: people round to a number that sounds reasonable, forget the mild ones, and merge two attacks that ran together. That’s why the diagnostic criteria are built to be counted day by day rather than recalled — and why they’re all written in the same three units. Chronic migraine is a headache-day count with a migraine-day count inside it. Medication-overuse headache is a medication-day count. Both are sustained over more than three months, so a single bad month can’t establish either, and a good one can’t rule them out.
The full method — what to log for every attack, what to note on clear days, and a template you can copy — is in our guide to keeping a migraine diary. This page does the last step of it: reading the monthly line.
Where the numbers come from
Every line on this page is from the diary guide, which quotes the International Classification of Headache Disorders (ICHD-3): 15 or more headache days a month with at least 8 migraine days for chronic migraine; 10 or more days a month of triptans, ergotamines, opioids or combination painkillers, or 15 or more days of simple painkillers, for medication overuse; more than three months for both; and one full month as the minimum for any monthly figure.
Two things are ours, and worth knowing which. “Within three days of the 15-day line” is where we flag that unlogged mild headaches could decide the answer — the guide says leaving them out is the most common way a diary undercounts, but gives no margin. And the note on mixing medication types is a flag, not a rule: the guide quotes the per-type lines only, so when your days mix types the page tells you to bring the split rather than guessing how they add up.
What this can’t tell you
It can’t diagnose anything, and it doesn’t try — the thresholds are for orientation, and a diary is something you bring to a clinician, not a substitute for one. It can’t say whether a preventive is working (that’s a change in monthly headache days after two or three months on the dose, and it’s your clinician’s read), whether there’s a menstrual pattern (three cycles of dated entries), or what your triggers are. If you suspect the weather, that one has its own four-box weather test.
And no count matters more than something new. A different kind of headache, a new symptom or a worst-ever attack gets said first at any appointment. A sudden, severe headache unlike any you’ve had is a reason for urgent care the same day, not a diary entry.
Frequently asked questions
How many migraine days a month is chronic migraine?
Under the International Classification of Headache Disorders (ICHD-3), chronic migraine is headache on 15 or more days a month for more than three months, with migraine features on at least 8 of those days. Below that it is episodic. Both halves matter: 15 headache days with only 4 that look like migraine does not meet the definition as written, though it is still a reason to be seen.
How many days of painkillers is medication overuse?
ICHD-3 defines medication-overuse headache by counting days of regular use for more than three months: 10 or more days a month of triptans, ergotamines, opioids or combination painkillers, or 15 or more days a month of simple painkillers such as paracetamol or NSAIDs. How a mix of types counts together is a question for your clinician. Don’t stop or change medication on your own because a count crossed a line — make that plan with your doctor.
Why won’t the calculator give a monthly figure from two weeks of diary?
Because doubling two weeks is a guess scaled up, not a count. A reliable headache-days-per-month figure takes one full month, and the chronic and overuse definitions are both written over more than three. Under a month the calculator shows the raw count only — the one exception is a medication line already crossed inside the part-month, since the rest of the month can only add to it.
Is the migraine days calculator free, and is my data stored?
It is free, there is no sign-up, and nothing you type leaves your browser. The counts are compared on your device and nothing is sent to a server.
The calculator reads one line. The diary writes ninety of them.
The hard part isn’t the arithmetic — it’s having honest counts, including the entry you’d have to make mid-attack. MigrainePal starts an attack with one tap so you can put the phone face-down and fill in pain, aura and meds later, and its calendar counts headache, migraine and medication days for you. On your device, no account.
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