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Ovulation Calculator

For awareness only. This calculator predicts based on cycle averages. It is not reliable contraception and not a substitute for medical advice. Cycles vary — fertile windows can shift.
First day of last period
Cycle length28 days
From day 1 of one period to day 1 of next
Period length5 days
How long bleeding typically lasts
Ovulation typically occurs 14 days before your next period. Fertile window is the 5 days before plus the day of ovulation.
Read the guide
BBT Charting Basics — How the Thermal Shift Confirms Ovulation

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About Ovulation Calculator

Track your menstrual cycle, predict fertile window and ovulation. Free online ovulation tracker.

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