The cycle length refers to the number of days from the beginning of one menstrual cycle to the beginning of the next. So in other to calculate your cycle length, count the number of days from the beginning of one menstrual cycle to the beginning of the next. Having done that, it is important that you observe your cycle length for at least six months and subtract the shortest cycle length you recorded from the longest cycle length you recorded. If the difference between the two cycle lengths is more than 5 days, then it is likely that you are not ovulating regulalrly in all the cycles but if it is less than or equal to five days, then the chances are that you are ovulating regularly in most if not all your menstrual cycles. To learn more about cycle length, regular and irregular menstrual cycles, please read the article NORMAL AND ABNORMAL MENSTRUAL CYCLES or CHAT WITH OUR COCNSULTANTS.