How Does the Menstrual Cycle Work?
The menstrual cycle is the monthly process that prepares the body for a possible pregnancy. It's counted from the first day of bleeding until the day before the next period.
A normal cycle lasts between 21 and 35 days, averaging 28 days.
Phases of the Menstrual Cycle
1. Menstrual Phase (days 1-5)
The uterine lining sheds, causing menstrual bleeding. Typically lasts 3-7 days.
2. Follicular Phase (days 1-13)
Follicles in the ovaries begin to mature. Estrogen levels rise.
3. Ovulation (day ~14)
Ovulation day = Cycle length - 14 days
A mature egg is released from the ovary. This is the peak fertility moment.
4. Luteal Phase (days 15-28)
The body prepares for possible pregnancy. If no fertilization occurs, a new cycle begins.
Fertile Window
The most fertile days are the 5 days before ovulation and ovulation day itself. Sperm can survive up to 5 days in the reproductive tract.
This calculator provides estimates based on regular cycles. It should not be used as a contraceptive method. Consult your doctor for family planning.
Not necessarily. Any length between 21 and 35 days is normal. What matters is that it's relatively consistent month to month.