The 31st menstrual period to project when ovulation is, such as regular menstruation for 28~30 days, ovulation for the next month 14~16 days, such as irregular menstruation, you can use ovulation test paper or cervical mucus and other methods to project. Ovulation projection needs to be based on personal menstruation is regular to carry out, commonly used formula projection method, ovulation test paper self-test method, cervical mucus method. 1. Formula projection method: regular menstruation, if May 31 for the first day of menstruation, June 30 for the first day of the next menstrual period, the day of ovulation for the first day of the next menstrual period minus 14 days, then June 16 for the day of ovulation. 2. Ovulation test paper self-testing method: generally in the third day after menstruation clean start testing, until the test paper shows two bars as deep, on behalf of 24 hours to 48 hours will be the day of ovulation. 3. Cervical mucus method: according to the cervical mucus trait observation, generally the cervical mucus becomes clear, high degree of filamentation and is not easy to break, this trait lasts between the last day of 48 hours for the ovulation period. The exact time of ovulation needs to be determined under the guidance of a doctor.