How to Count Menstrual Cycle Days

A young woman using a tablet computer in her bedroom.

Tracking your menstrual cycle can be important for a number of reasons. These include determining your normal pattern, which can help you identify changes that could signal a problem. Counting your menstrual cycle days also helps you identify your most likely fertile period to prevent pregnancy or enhance your chances of conception. Menstrual tracking is simple, requiring only a calendar or electronic tracking method.

Normal Cycle Variation

Women’s menstrual cycles may vary considerably. Although the so-called normal cycle is 28 days, many healthy women have periods as frequently as every 22 days or as infrequently as every 36 days, according to the authors of a May 2006 article published in the "Journal of Obstetric, Gynecologic and Neonatal Nursing." The length of menstrual bleeding also varies from 4 to 7 days. Menstrual cycle length and flow may also vary from one cycle to the next in the same woman. Stress and illness are among the many possible reasons for a variation in the menstrual cycle from one month to the next.

Counting the Days

To track your menstrual cycle, note the first day of your period on a calendar or electronic device. Online applications are also available to help you track it. Note the number of days you experience bleeding, which will help you determine the average length of your menstrual flow. Continue to count days until your next period occurs and note the total number of days between the beginning of 1 period and the beginning of the next. This is your menstrual cycle length. Continue to track your periods for several months until you determine your usual cycle.