Period Calculator
Enter your last period, cycle length and how long your period usually lasts to predict your next six periods — start and end dates for each.
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How period prediction works
Your cycle length is counted from the first day of one period to the first day of the next. This calculator simply projects that rhythm forward six cycles, so you can plan travel, events and appointments. Real cycles drift a day or two either way — the further out the forecast, the wider the real-world wiggle room.