The best time to measure ovulation depends on whether you are using ovulation test strips to measure ovulation or monitoring ovulation under ultrasound, the time varies depending on the method. If ovulation is monitored with ovulation test paper, if your period is regular and your cycle is about 28 days, you can start monitoring around the 10th day of your period, do not drink water before the test, and preferably monitor at a fixed time every day, if the test is positive, it indicates ovulation within a day or two, but not all women are suitable for this method. If ovulation is monitored under ultrasound, for women with regular cycles of about 28 days of menstruation, it is also recommended to start monitoring around the 10th day of menstruation, if the follicle is only about 10 mm, it can be monitored again in about three days, generally the follicle may grow by about 1 mm daily, if the follicle is about 16 mm, it can be monitored again every other day, if the follicle reaches about 18 by 18 mm it indicates a dominant If the follicle reaches about 18 by 18 mm, it indicates a dominant follicle, and ovulation may occur in the next two days or so, so you can continue monitoring once the next day. In conclusion, the best time to measure ovulation is from around the tenth day of menstruation. You can also determine whether a woman is ovulating based on whether she has egg-white-like leucorrhea.