How to use the period calculator
Enter the first day of your last period and your average cycle length (count from the first day of one period to the first day of the next). The calculator predicts your next 3 periods, your fertile window (the 6 days when pregnancy is most likely) and your ovulation day (usually 14 days before your next period).
Why track your cycle?
Knowing your cycle helps you plan around your period, understand PMS symptoms, and identify your most fertile days whether you are trying to conceive or avoid pregnancy. Pair it with our ovulation calculator for a fuller picture.