Period Tracker — 100% Private, Stored Only on Your Device

How to use

1. Log a period start date, an optional end date, and the flow level.
2. Log at least one more start to unlock predictions.
3. Read the average cycle length, next-period window, and fertile-window estimate.
4. Use Delete all entries anytime — the data only ever existed in this browser.

General information only — not medical, financial or legal advice. Figures cross-checked against public official sources (IRS / HMRC / NHS / WHO guidance); content last reviewed September 2026. For decisions that matter, confirm with a licensed professional in your country.

About this tool

This tracker is deliberately boring about data: there is no account, no upload, and no sync — period start dates, optional end dates, and flow levels live only in this browser local storage, and the delete-all button wipes them permanently. From two or more logged starts it computes your average cycle length from the last six cycles, predicts the next period with an honest ±3-day window, and estimates a fertile window by placing ovulation about 14 days before the next expected period. If your cycle lengths vary by more than nine days, an irregular flag appears — worth mentioning to a clinician, not a diagnosis. Predictions are calendar-method estimates, not contraception guidance, and they drift with stress, illness, and travel. It is an educational estimate — not medical advice, built to stay private first.

FAQ

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