Women if menstruation is regular, the 11th to menstruation ovulation generally between the 22nd of this month to the 1st of the next month, if menstruation is not regular, ovulation will change. 1. Regular menstruation: If a woman’s menstruation is usually regular, the day of ovulation is usually 14 days before the next menstrual period, and it is possible to ovulate 5 days before and 4 days after the day of ovulation, with a menstrual cycle of 30 days, for example, the 11th comes to menstruation, and ovulation should be between the 22nd of this month and the 1st of the next month. 2. Irregular menstruation: If a woman’s menstruation is usually irregular, the ovulation period will change and can not be calculated according to the 14 days before the onset of menstruation, the specific ovulation period can be based on the basal body temperature measurement and ultrasound monitoring to project.