The average menstrual cycle length is 28 days, but that's just an estimation. It's common for cycles to range from 21 to 45 days, according to WomensHelth.gov. Teens, women with hormone imbalances, women with medical conditions like polycystic ovarian syndrome or women approaching menopause might encounter cycles longer or shorter than those averages. For those women, an average cycle length can be established with a few months of record keeping.
Step 1
Circle the first day of your menstrual cycle on the calender. Write "cycle day 1" below the date.
Step 2
Number each of the days after day 1, until you get your period again. The day before your period is the last day of your cycle, and day one starts over again on the first day of your next period.
Step 3
Record your cycle days for three to six months. The longer you record, the more accurate your average cycle length will be.
Step 4
Add together the number of cycle days in each month, and divide by the total number of months. For example, if your first cycle was 28 days, your second cycle was 27 days and your third cycle was 26 days, add 28, 27 and 26 together to get 81. Divide 81 by 3 for the three months you're averaging. Your average cycle length in this case is 27 days.
Things You'll Need
- calender
