How to Use a Menstrual Cycle Calculator
Using a menstrual cycle calculator will help you to learn more about your body and also to predict when you are most fertile. This information can help you to either avoid or encourage pregnancy. Additionally, knowing when to expect your next period might be helpful in making other decisions, as well–like when to schedule a vacation so that it will not coincide with your period.
Get some graph paper. The vertical axis will represent your temperature reading. Write the numbers 97.5 through 99.5, including each tenth of a degree, on this vertical axis.
Make the horizontal axis at the bottom of the graph the number of days in your cycle. On this axis, write the numbers one through twenty-eight leaving room for additional numbers in the event that your cycle runs longer than 28 days. The top horizontal axis should represent the actual day of the year; for instance, “June 3, 2008.”
Begin charting your cycle on the first day of your next period. This day represents cycle day 1. Beneath the numbers on the horizontal axis that represent each cycle day, write a letter “M” to indicate that you are menstruating. Do this for each day that you have your period during this cycle.
Be prepared to start taking your oral temperature by cycle day 2. Do this the first thing in the morning after a solid block of sleep, preferably at the same time each morning, before you get out of bed and even before you go to the bathroom. Use a basal body temperature thermometer to do this–a regular thermometer that you use to read a fever is not sensitive enough.
Draw a small dot next to the number on the vertical axis that corresponds with your temperature reading. This dot should also be in line with the corresponding cycle day number and date on your horizontal axis. Do this every day and connect the dots with a straight line as the days go by.
Determine your ovulation day. If you notice a rise of about 0.4 degrees F in your basal body temperature that sustains itself for at least 3 days, then you probably ovulated on the day before the first temperature rise. Go back in your chart and draw brightly colored crosshairs on that day.
Expect your period to arrive anywhere from 10 to 16 days after ovulation. This phase in your cycle after ovulation but before menstruation is called the “luteal phase.” The luteal phase is usually consistent from cycle to cycle for the same woman. In other words, once you have used your menstrual cycle calculator for a few months and you see how long your luteal phase lasts, you can expect it to last for about that same amount of time each month.
