Ovulation Calculator

To calculate the days in a month when you are most likely to conceive, use the table below to enter your menstrual history information. Please keep in mind that as all women are individual, all women's ovulation cycles are individual, which means you can use this calculator as a guide, but it is by no means exact.

Your date of ovulation is calculated by subtracting 13 to 17 days from the date of your next period. A reminder that again, this is an approximation. The calculations may be further off if your cycles are less than 21 days long or longer than 35 days, or if your menstrual cycles are irregular from month to month.

Please consult your health care provider for more information, and/or learn more about your fertility cycles from these books:

- Your Fertility Signals, by Merryl Winstein
- The Billings Method, by Dr. Evelyn Billings and Ann Westmore
- Taking Charge of Your Fertility, by Toni Weschler

Enter the first day of your last period: