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
Dec 27, 2018Dec 23 - Dec 31Dec 23 - Dec 28Jan 10, 2019Jan 5, 2019Sep 20, 2019
Jan 24, 2019Jan 20 - Jan 28Jan 20 - Jan 25Feb 7, 2019Feb 2, 2019Oct 18, 2019
Feb 21, 2019Feb 17 - Feb 25Feb 17 - Feb 22Mar 7, 2019Mar 2, 2019Nov 15, 2019
Mar 21, 2019Mar 17 - Mar 25Mar 17 - Mar 22Apr 4, 2019Mar 30, 2019Dec 13, 2019
Apr 18, 2019Apr 14 - Apr 22Apr 14 - Apr 19May 2, 2019Apr 27, 2019Jan 10, 2020
May 16, 2019May 12 - May 20May 12 - May 17May 30, 2019May 25, 2019Feb 7, 2020


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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/