how to work out my cycle length
To calculate menstrual cycle length, you count the number of days from day one of your period (CD 1) up to, and including, the day before the next period starts. The count does not include the first day of the next menstrual period, because that's Cycle Day 1 of the next cycle. Your average cycle length displays. 2  Each time you track your next period, your cycle length is updated! 3  Use My History/Quick History, or the Menstrual Cycle Chart, to see your average, shortest and longest menstrual cycle length.