How to Read a Basal Body Temperature Chart

A basal temperature chart can help you pinpoint ovulation. Reading the charts can be tricky, though, and does take practice and dedication. If you'd like to be aware of when you ovulate to increase your chances of pregnancy, or to try to avoid one, knowing how to read the chart correctly can increase your chances of success.

Things You'll Need

• Basal thermometer
• Basal temperature chart
• Pen or pencil

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Instructions

Reading Your Basal Temperature Chart

• 1

  Record waking temperatures to establish a pattern. Use your basal thermometer to take your temperature at approximately the same time every morning. You can take your temperature orally, rectally or vaginally, but most women find that taking their temperature orally is easiest. Record your temperature on your basal temperature chart. Usually, charts have temperatures on the left-hand side of the page, with dates on the bottom. Find the current date, and mark the temperature above that date. You can use a paper chart or an online charting service, such as FertilityFriend.com.

• 2

  Search for a thermal shift, which indicates that ovulation has occurred. Look for three consecutive temperatures that are above the previous six. John and Sheila Kippley, authors of "Natural Family Planning," say that the temperatures should be at least four-tenths of a degree higher than the previous six. Once your temperature rises approximately four-tenths of a degree, it should stay raised until you menstruate again. This is because of the elevated levels of progesterone that are released after ovulation.

• 3

  Determine the day of ovulation. The day you ovulated is most likely the day immediately before your first elevated temperature. An egg lives for only 12 to 24 hours, the Kippleys say, so if you are trying to conceive, time your intercourse before or during ovulation, not after.

• 4

  Use hindsight to achieve or avoid a pregnancy. When you're first learning how to read your basal chart, it can be hard to predict when you will ovulate, so take your temperature for a few cycles to determine if there's a pattern. Once you've established a pattern, you can better time your intercourse. Keep in mind that sperm can live for three to five days and, in some cases, up to seven days, the Kippleys state.