Ovulation usually occurs about 14 days before the next menstrual period. Therefore, if a woman with regular periods has her period on the 25th, ovulation should occur around the 10th of the following month. However, if the period is irregular and it is difficult to calculate the ovulation time, it is better to monitor ovulation under ultrasound. Ovulation calculation is only applicable to women with regular menstruation. You need to know a woman’s menstrual cycle, the date of the first day of menstruation, and then push forward 14 days from the next menstrual period to the day of ovulation, and 5 days forward and backward from the day of ovulation, during which 10 days is the ovulation period. However, since the hormone level in each person’s body is different and the menstrual cycle varies, ovulation cannot be fixed. When menstrual cycles are irregular, ovulation can be monitored by ovulation test strips or ultrasound for more accurate results. It is recommended that women who wish to get pregnant should arrange intercourse during ovulation to increase the chances of pregnancy. However, if you do not want to get pregnant, it is recommended to use contraception when having intercourse to avoid unwanted pregnancy.