Ovulation is usually about 14 days before the next menstrual period. If the last menstrual period is on the 27th, and the usual menstrual period is regular with a 30-day cycle, the ovulation day will be about the 13th of the following month. Ovulation should be calculated according to the menstrual cycle and the last menstrual period, and the exact time of ovulation is related to the usual menstrual cycle. If the patient has regular menstruation and has her period on the 27th, the ovulation day will be the 13th of the following month. 4 days before and 5 days after the 13th is the ovulation period, when the chance of conception is higher. If you don’t have a plan to get pregnant, you should take birth control measures during ovulation. However, the menstrual cycle is affected by mental factors and work stress, which affect ovulation, so women with irregular periods cannot project ovulation based on their last menstrual period. If you are planning to get pregnant, you can combine ovulation test paper or ultrasound to monitor ovulation at the same time to help improve the chance of conception. Usually, you should pay attention to maintain a regular life and try to make your menstrual cycle as normal as possible to help obtain a normal ovulation period.