How to Calculate Coverline

Many women chart their temperatures to keep track of when they are fertile. The coverline is the highest temperature a woman experiences before she ovulates. Determining the coverline during a cycle is important because it marks the shift from the pre-ovulatory phase to the post-ovulatory phase. This information is especially important when practicing natural family planning to avoid or achieve pregnancy. It usually only takes a few cycles of practice to learn how to accurately calculate your coverline; however, it may take longer if you tend to have erratic temperatures.

Things You'll Need

• Basal Body Thermometer
• Chart or Graph

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Instructions

• 1

  Wake up at the same time every morning and take your temperature before getting out of bed. This temperature reading is known as your basal body temperature, which is the temperature of your body at rest.

• 2

  Record your temperature on the chart or graph. Be sure to record your temperature immediately after taking it to avoid the possibility of forgetting what it was later.

• 3

  Complete a full cycle. A full cycle begins on the first day of your period and ends on the first day of the next period.

• 4

  Examine you temperatures. In a healthy ovulatory cycle, you should notice a shift in your daily temperatures approximately two weeks from the end of the cycle. According to the National Women's Health Information Center, after you ovulate, your temperature increases by at least .4 degrees and remains elevated for at least three consecutive days. On most charts it is easy to see the general area where the thermal shift occurred.

• 5

  Look at the six temperatures preceding the thermal shift. Find the highest of the six temperatures and add one-tenth of a degree to it. This temperature is your coverline.

• 6

  Repeat these steps for a couple of more cycles. Eventually, you will be able to determine your coverline before the end of the cycle. Women who have regular cycles may be able to compare their charts and coverlines to predict ovulation reasonably within a few days.