A period calculator helps to estimate the time of the next menstruation, taking into account the most probable days of menstruations. During the proce ss called ‘ovulation’, the lining of the uterus thickens and an egg is produced which is required for getting pregnant. A woman is fertile during this time, i.e, five days before ovulation and a day or two after ovulation. But if this egg is not fertilized or in other words if the woman doesn’t get pregnant, then the egg gets flushed out of the body along with blood known as Menstruation or Periods. It is a regular discharge of blood and mucosal tissue that happens during the menstruation cycle. The menstruation cycle begins on the first day of the period and is counted until the start of the next period, normally 21-35 days. A Period Calculator is also helpful to decide ovulation. Determining ovulation which is before periods can help one plan for their pregnancy. When a woman gets pregnant, the egg gets fertilized, otherwise, the bleeding and discharge of blood and mucosal tissue occur through the vagina disposing of the egg. The Period calculator considers these cycles that last for 5-7 days. The period does not appear during pregnancy and menopause. To find out whether or not a woman is pregnant or not, her last period date is considered. For medical and many other reasons, knowing the last period date is important.