Menstrual cycle

Your cycle is more than the days you bleed. These guides explain the phases from one period to the next, what usually changes along the way, and how much variation from month to month is common.

Guides

• How Long Is a Normal Menstrual Cycle?Most cycles last 21 to 35 days, and few are exactly 28. What large studies show about cycle length by age, how much variation is typical, and when to ask.
• What Are the Phases of the Menstrual Cycle?The four phases of the menstrual cycle explained: typical days, the hormones behind each one, and why real cycles rarely follow the 28-day textbook.

Tools

• Period calculatorEstimate your next six periods, with start and end dates, from your last period, cycle length and period length.
• Cycle length calculatorWork out your average cycle length, shortest and longest cycle, and how much it varies from your period start dates.

These guides are general wellness information, not medical advice. If something about your cycle or your health worries you, talk to a doctor or midwife.