Generally, a woman has 5 to 7 days of a menstrual period. It is different from any girl. In my case, my monthly period lasts from 3 to 5 days. But another girl might have longer periods than the average.
As long as a woman is not pregnant and is not using hormonal contraceptives, the period usually is a sign that one menstrual cycle has finished and the next one has started. In most women, the period lasts 3 to 5 days.
