Most people use a menstrual calculator not because they expect a perfect medical answer, but because they want help with everyday planning. When might the next period arrive, which dates may need extra preparation, where might ovulation fall, and what phase am I probably in right now? This page is best used for that calendar-level kind of prediction.
It can help with reminders, travel planning, supply preparation, and basic fertility awareness. It is not a substitute for a doctor, hormone testing, basal body temperature tracking, or a more detailed fertility method. Keeping that boundary in mind is part of using the page well.
This is the starting point for the entire prediction chain. The current page does not allow a future date here because it is supposed to represent the most recent actual period start. If this date is off by a few days, the rest of the predicted timeline shifts with it.
The current page accepts cycle lengths from 21 to 35 days. It uses that value to project the next period start date, so shorter cycles lead to earlier predictions and longer cycles push the next period later.
It is best for period planning, travel preparation, and rough ovulation-window reference rather than medical evaluation.
The current page first predicts the next period from cycle length and then places ovulation 14 days before that date.
Not completely. The current implementation still uses fairly fixed day ranges for phase labels, so it is better used as a rough guide.
No. It is better for calendar-level reminders, and concerns about contraception, fertility, pain, or irregular cycles should still go through a clinician.
Predict your menstrual cycle and ovulation, understand your body's rhythm