Period Tracker

Tap Period started on the day your period begins and Period ended when it stops. For an earlier period, pick its first day in the date box and tap Period started; it is filled in with your usual length. Tap any day on the calendar to mark it as a period day or not, and to add flow, symptoms or a short note. Days a day or two apart count as one period.

Your average cycle is the time from the start of one period to the start of the next, over your last 6 cycles, and your average period works the same way. Until you have logged two periods it uses 28 and 5 days. The next period is estimated by adding your average cycle to the start of your last one. Gaps under 15 or over 90 days are left out of the averages, since a period was probably not logged.

The fertile window, off unless you turn it on, is a rough estimate: about 5 days before to 1 day after a likely ovulation, 14 days before your next period. It is not reliable enough to prevent or plan a pregnancy.

These are estimates, not medical advice. Irregular cycles are common, and stress, travel, illness and many other things can move a period by days or weeks. If something worries you, a doctor or nurse can help.

Everything stays in this browser on this device: nothing is sent anywhere, and there is no account or analytics. Export JSON keeps a full copy you can import again later; Export CSV opens in a spreadsheet. Delete all data removes everything this tracker saved, with a few seconds to undo.