Ovulation Calculator

The Ovulation Calculator estimates the ovulation date and the corresponding due date if the pregnancy is based on normal biological cycles. It is not recommended to avoid pregnancy based on ovulation calculation.

First Day of Your Last Period:
Average Length of Cycles:
 

Most Probably*Ovulation WindowEstimated Due Date if Pregnant
Sep 18, 2015Sep 14, 2015 - Sep 24, 2015Jun 11, 2016
Oct 16, 2015Oct 12, 2015 - Oct 22, 2015Jul 9, 2016
Nov 12, 2015Nov 8, 2015 - Nov 18, 2015Aug 6, 2016
Dec 10, 2015Dec 6, 2015 - Dec 16, 2015Sep 3, 2016
Jan 7, 2016Jan 3, 2016 - Jan 13, 2016Oct 1, 2016
Feb 4, 2016Jan 31, 2016 - Feb 10, 2016Oct 29, 2016

* This date is based on the average of 14 days before the next period was due.


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Ovulation is the process by which a mature ovarian follicle ruptures and discharges one or a few eggs in a female's menstrual cycle. This process is controlled by the brain via the release of the luteinizing hormone (LH) and the follicle-stimulating hormone (FSH). If the egg is fertilized by sperm, it may implant from 6 to 12 days later, at which point pregnancy begins.

The average ovulation time is 14 days before the first day of your next period. However, the ovulation day may vary among women. Therefore, cycle length alone is not a reliable indicator of your ovulation day. Ovulation tests are more accurate, having a 99% accuracy rate, and they can be purchased without a prescription.

Normally, ovulation test kits measure the LH level in urine. A surge of the LH level, or a "positive" test result indicates the onset of ovulation and the fertilization windows, which occur during the following three days.