How many days does a girl usually have her period?

Under normal circumstances, the duration of menstruation for girls is about 3-5 days, less than 3 days or more than 7 days is abnormal. Menstruation is bleeding caused by endometrial shedding every month. Menstruation has certain rules, normal menstrual cycle is generally 21- 3 - 5 days, 1 week ahead or 1 week late is normal. Normal menstrual blood is dark red, bleeding volume is about 50mL per month, less than 30mL or more than 80mL, which is abnormal. Regular menstruation is important for normal follicle development. If menstruation shows disorders, it may affect follicle development and may also affect normal pregnancy.