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
Oct 7, 2018Oct 3 - Oct 11Oct 3 - Oct 8Oct 21, 2018Oct 16, 2018Jul 1, 2019
Nov 4, 2018Oct 31 - Nov 8Oct 31 - Nov 5Nov 18, 2018Nov 13, 2018Jul 29, 2019
Dec 2, 2018Nov 28 - Dec 6Nov 28 - Dec 3Dec 16, 2018Dec 11, 2018Aug 26, 2019
Dec 30, 2018Dec 26 - Jan 3Dec 26 - Dec 31Jan 13, 2019Jan 8, 2019Sep 23, 2019
Jan 27, 2019Jan 23 - Jan 31Jan 23 - Jan 28Feb 10, 2019Feb 5, 2019Oct 21, 2019
Feb 24, 2019Feb 20 - Feb 28Feb 20 - Feb 25Mar 10, 2019Mar 5, 2019Nov 18, 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/