How to Calculate the Days of a Cycle

A woman's menstrual cycle varies in length. On average, a woman's cycle is 28 days in length, but can range anywhere from 21 to 35 days in length. By counting the days of your monthly cycle, you can try to determine when ovulation will occur. Ovulation occurs when the ovaries release an egg for fertilization. You can also count the days between menstrual periods to determine the length of your menstrual cycle.

Things You'll Need

• Calendar

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Instructions

• 1

  Obtain a calendar in which to chart your monthly cycles.

• 2

  Mark the first day of menstrual bleeding in your calendar. This day represents day one of your monthly cycle.

• 3

  Keep track of your menstrual periods for two months. Each month mark the first day you start to bleed on your calendar.

• 4

  Look at your calendar and locate the day you started bleeding in the second month.

• 5

  Count backwards on your calendar 14 days from the first day you started bleeding during your second calendar month. If you count backwards 14 days, you can determine the possible day you ovulated.

• 6

  Use your calendar to calculate the total number of days in your monthly cycle. Count from the beginning of one menstrual period to the beginning of the next menstrual period.

• 7

  Try to determine the day when your next month's menstruation will begin. If your monthly cycles are fairly regular -- for example, occurring about every 30 days -- then you can predict that 30 days after the start of one month's menstruation your next menstruation will begin.