Ovulation is a period of 10 days that includes the day a woman ovulates, the 5 days before and the 4 days after the day of ovulation. During this time period, women ovulate and are prone to conceive after intercourse. There are several methods to calculate ovulation: 1. The most common method is to calculate ovulation through the menstrual cycle. If the menstrual cycle is regular, the ovulation day is about 14 days before the next menstrual period, and the 5 days before and 4 days after the ovulation day belong to the ovulation period; 2. Ovulation. The most accurate way to observe ovulation is to monitor follicle development and ovulation by ultrasonography.