Ovulation Calculator

The Ovulation Calculator estimates most probable ovulation date as well as other related. The estimations are calculated using information such as the first day of a person's last period and the average length of their menstrual cycles in conjunction with what is known regarding typical biological cycles. This calculator should not be used as a form of birth control.

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

Most Probable Ovulation DateOvulation WindowFertile WindowNext PeriodPregnancy TestDue Date if Pregnant
May 6, 2018May 2 - May 10May 2 - May 7May 20, 2018May 15, 2018Jan 28, 2019
Jun 3, 2018May 30 - Jun 7May 30 - Jun 4Jun 17, 2018Jun 12, 2018Feb 25, 2019
Jul 1, 2018Jun 27 - Jul 5Jun 27 - Jul 2Jul 15, 2018Jul 10, 2018Mar 25, 2019
Jul 29, 2018Jul 25 - Aug 2Jul 25 - Jul 30Aug 12, 2018Aug 7, 2018Apr 22, 2019
Aug 26, 2018Aug 22 - Aug 30Aug 22 - Aug 27Sep 9, 2018Sep 4, 2018May 20, 2019
Sep 23, 2018Sep 19 - Sep 27Sep 19 - Sep 24Oct 7, 2018Oct 2, 2018Jun 17, 2019


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Ovulation and Conception

Ovulation in humans is the process by which ovarian follicle(s) rupture and release a mature egg from the ovaries. On average, ovulation occurs within the 4 days before or after the midpoint of a woman's menstrual cycle (14 days before the start of a woman's next menstrual period). Menstrual cycles vary between women however, and a person without a 28-day menstrual cycle may need to track their menstrual cycle to more accurately determine when ovulation might occur.1 It is also possible to use an over-the-counter ovulation test that tests for a surge in some specific hormones that precede ovulation by 24-48 hours. While these tests are 99% accurate in detecting the specific hormones, they cannot guarantee when exactly ovulation will occur within the two-day period.2

Day 10-18 of the menstrual cycle (on average) is the most fertile phase of the menstrual cycle. This is important when trying to conceive because fertilization of the egg can only occur for 12-24 hours after release during part of the luteal phase, when a mature egg travels through the fallopian tubes towards the uterus. Since sperm can survive inside a woman's body for up to five days, regular sex five days before and on the day of ovulation can improve the likelihood of conception.1 If fertilized, the egg will implant in the uterus 6-12 days later. Otherwise, menstruation occurs, and blood and mucosal tissue from the inner lining of the uterus is expelled.


  1. Mayo Clinic. 2016. "What ovulation signs can I look out for if I'm hoping to conceive?" www.mayoclinic.org/healthy-lifestyle/getting-pregnant/expert-answers/ovulation-signs/faq-20058000.
  2. American Pregnancy Association. 2016. "Ovulation Kits & Fertility Monitors." americanpregnancy.org/getting-pregnant/ovulation-kits/