First of all, we need to know our basal body temperature. An increase of 0.3℃-0.5℃ in body temperature on the basis of the basal body temperature represents ovulation, you can make an Excel sheet or coordinate chart first, and start measuring the basal body temperature from the first day of menstruation. Every day, wake up early and do not engage in any activities after waking up, including getting out of bed, going to the toilet, brushing your teeth and washing your face, which means that you should measure your underarm temperature in a quiet state. Through the above description, you can know how to determine the basal body temperature and the key points to pay attention to during the process of determination. In addition to measuring the basal body temperature, you can also monitor ovulation by doing ultrasound.