Most women who menstruate have a period about once a month, typically every 21–35 days, with an average around 28 days. The actual bleeding usually lasts about 3–7 days each time.

Basic cycle timing

  • A menstrual cycle is counted from the first day of one period to the first day of the next.
  • For most adults, “normal” cycles are roughly every 21–35 days, with many people close to 28 days.
  • Teenagers often have longer or more irregular cycles at first, which usually become more regular with age.

How long a period lasts

  • Bleeding itself usually lasts between 2 and 7 days, with about 4–5 days being most common.
  • Flow is often heaviest in the first 1–2 days and then gets lighter.

How many years of having periods

  • Many women have periods for about 40 years of life, from puberty until menopause.
  • Menopause is defined as 12 months with no period, most often between ages 45 and 55.

When “often” is too often or too rare

  • Periods more often than every 21 days or less often than every 35–38 days can be a sign to check in with a doctor.
  • Very heavy bleeding, bleeding between periods, or sudden big changes in your usual pattern also deserve medical advice.

Forum-style note

On health forums and women’s communities, people often share that “normal” is a wide range, and what matters most is your own regular pattern rather than matching a perfect 28‑day cycle.

If your period is coming much more frequently or rarely than this, or your pattern has changed suddenly, a healthcare professional can help work out what is going on.