How to Calculate Days in a Menstrual Cycle

Calculating the length of your menstrual cycle is important to your health for a variety of reasons. If you are trying to get pregnant or concerned about reproductive health for any reason, your doctor will want to know how long your cycle is. A healthy cycle can last anywhere from 23 to 35 days; if your cycle is significantly longer or shorter than this range, it is a good idea to consult with a gynecologist to rule out potential health problems. However, in order to gauge whether your cycle is abnormal, you need to know how to correctly calculate your cycle length.

Things You'll Need

• Calendar or note pad

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Instructions

• 1

  Begin counting the first day of bleeding; this is known as "cycle day one." Mark the date on a calendar or note pad, so you remember the specific date.

• 2

  Continue counting until the first day of your next period, or the next "cycle day one." The number of days in between each "cycle day one" is the length of your menstrual cycle. For example, if your period begins on January 1, and your next period begins on January 28, your cycle length is 27 days.

• 3

  Repeat this process for four to five cycles, marking the first day of bleeding each month as the point that counting should reset. Use this set to find your average menstrual cycle length; this average will be more accurate than simply counting the length of one cycle.