Free tool to calculate ovulation date, fertile window, and conception chances. Accurate calculation based on your menstrual cycle.
All calculations happen in your browser. Your data is not sent to servers.
To calculate ovulation:
⚠️ Important! This calculator provides an estimate. For more accurate ovulation tracking, use ovulation tests, measure basal body temperature, or consult a gynecologist. Irregular cycles reduce calculation accuracy.
With an irregular cycle, track ovulation using ovulation tests, measure basal body temperature, or use cycle tracking apps. The calculator will be less accurate as it relies on average values.
The fertile window lasts about 6 days: 5 days before ovulation and the ovulation day itself. Sperm can survive up to 5 days, while the egg remains viable for about 24 hours after release.
You can identify ovulation by:
Ovulation calculation is based on the average length of the luteal phase of the menstrual cycle, which is 14 days. This means ovulation occurs 14 days before the next period starts. In a standard 28-day cycle, ovulation occurs on day 14. With longer or shorter cycles, the ovulation day shifts accordingly.
Sources: American College of Obstetricians and Gynecologists (ACOG), World Health Organization (WHO)
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