The physiological period is calculated from the first day of menstruation to the first day of the next menstruation, which is a menstrual cycle, usually the majority of women’s menstrual cycle is 28-30 days once. Calculation of ovulation, in the clinic to calculate the time of ovulation, the time of ovulation is basically in the next menstrual period 14 days before, in the time of ovulation before 4 days and after 3 days, a total of 8 days is the time of ovulation, in the clinic so calculated. Of course, the calculation of the ovulation period must be based on the regularity of menstruation, if the menstruation is not regular, the calculated ovulation period is also inaccurate. Therefore, it is recommended that if you have irregular periods and want to know about ovulation, we suggest that you use ultrasound to find out and use it to calculate the ovulation period.