Write down the first day of your period or note it on a calendar.
Your period cycle, or menstrual cycle, is a key aspect of your health and tracking its length will help you manage your overall gynecological health. Although the most obvious reasons for calculating your menstrual cycle are estimating your due date for pregnancy or tracking the rhythms of your fertility, particularly long or short menstrual cycles can indicate serious health problems.
Instructions
1. Write down the date your period begins in your notebook or note it on your calendar. This should be the first day you notice bleeding, even if it's only spotting.
2. Jot down the date your next period starts or note it on your calendar. Count the number of days from the first day of your last period to the day before the start of this period. This is the length of your most recent cycle. Do not count the first day of this period, even if your period didn't start until late in the day, because the first day of this period is the first day of your current cycle rather than the last day of your previous cycle.
3. Continue calculating the lengths of your next four or five cycles. Remember, you will always count the first day of your previous period and the last day before your next period starts as part of the same cycle.
4. Add up the lengths of the four or five periods you've tracked. Divide them by the total number of periods you've tracked. This is your average menstrual cycle length. Although the average menstrual cycle length is 28 days, it is still considered normal to have a cycle that is anywhere from 21 to 35 days. If you are a teenager, your cycle may be as long as 45 days. If your average menstrual length falls outside this range, it may be nothing to worry about, but call your doctor to be sure.
5. Write down the length of your shortest and longest cycle. Update this information if you have a shorter or longer cycle later. A cycle that is significantly longer than either your average cycle length or your longest previous cycle may be symptomatic of a problem.
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