How to Calculate Menstrual Cycle Timing

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There are several reasons why you, as a woman, might choose to calculate your menstrual cycle. Perhaps you are anticipating a vacation or other time when it would be inconvenient to have your menstrual period, or you are trying to conceive. Knowing your menstrual cycle will also allow you to time intercourse for days when you aren’t fertile, as a natural birth control method.

To calculate menstrual cycle timing, you need to watch for three signs.


One of the most common ways to calculate a menstrual cycle is to chart the basal body temperature (BBT). This is done by using a special BBT thermometer, which measures temperatures to 1/10th of a degree, first thing in the morning. As soon as you wake up, and before you have had anything to eat or drink, you need to take your temperature. The temperature is then charted on a fertility chart.

Fertility charts can be handmade using graph paper or created online, and will allow you to track this and other aspects of your menstrual cycle.

Your waking temperature fluctuates based on where you are in your cycle. During the first half of the cycle, before you ovulate, your temperature will move up and down, several tenths of a degree, from one day to the next.

The day before ovulation, some women experience a dip in their temperatures. After ovulation, your temperature goes up and stays up until the first day of your period. After a month or two of charting, you should have a very accurate idea of the timing of your menstrual cycle.

Cervical Fluid

A woman’s cervical fluid also changes as she moves through her cycle, varying in consistency and color. After your period, your cervical fluid is dry and sticky, or even non-existent. Within a few days, the fluid becomes thick and cloudy, and then, leading up to ovulation, it becomes thin and clear, like egg white. After you ovulates, the cervical mucus starts to dry up again, becoming sticky and thick.

If you pay attention to the cervical fluid her body is producing, you can learn how to calculate your menstrual cycle using this sign. After washing your hands, reach up through your vagina to collect the mucus from right outside the opening of your cervix. Alternatively, wipe carefully, and then examine the fluid on the toilet paper.

Cervical Position

Monitoring your cervical position is the third way to calculate your menstrual period. Normally, your cervix is down low, firm and closed tightly, to keep bacteria from getting into your uterus. During your period, it opens slightly, and then returns to its closed position.

As you approach ovulation, the cervix rises up to the very top of your vagina, softens and opens up. If you have been checking daily, this will be a very noticeable change. After washing your hands, bend your knees and crouch down. This will allow you to more easily reach your cervix.

For comparison, a hard cervix will feel like the tip of your nose and a soft cervix will feel like the tissue between your thumb and index finger.

Keeping track of these signs will help you to calculate menstrual cycle timing for your own cycle. Even though 28 days is considered the average length of a menstrual cycle, with ovulation happening on day 14, this is not the case for every woman. A healthy cycle may vary from 21 days to 40 or more days, depending on a woman’s body. Knowing how to calculate where in your cycle you are can take a lot of the unpredictability out of being a woman.


Baby Hopes: Cervical Mucas– How it Relates to Your Fertility Cycle. From:

Taking Charge of Your Fertility: The Three Primary Fertility Signs FAQ. From:

Beyond Fertility: Cervical Position. From: