How to Chart Your Basal Body Temperature (BBT)

Some women know all too well how to chart their BBT, I have seen fertility blogs where a woman knows more about BBT than your average PhD in Biology. However, for those of us who encounter the concept for the first time, how do we do it?


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    The first thing you will need is a BBT thermometer. A regular glass thermometer will not work because it is not accurate enough to detect the small change in temperature.
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    Start your first measurement on the first day of your period (which is day 1 of your cycle). Use the thermometer to measure your BBT every morning, preferably at the same time. Since BBT is the lowest temperature of your body during rest, you need to measure your temperature right after you wake up and before you do any physical activity. You can measure orally or vaginally, as long as it is consistent.
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    Record your measurements every day. There are a variety of ways to do this. You could do it by hand, but the easiest way is to enter your temperature online so you can get an automatically generated chart. For an easy to use online BBT chart, check out
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    Reading the chart: Before ovulation, you will see a slight fluctuation in your temperature and it will usually range between 97.0 to 97 °F (36.1 to 36.1 °C). Right before ovulation, there might be a noticeable dip in the temperature, and then it will start to rise when ovulation occurs. After ovulation, the temperatures will generally be between 97.6 and 98.6. This pattern is called the bipastic phase because it has two stages. If there is conception, the temperature will rise even higher, beginning a third phase. If there is no conception, the temperature will begin to drop.


  • If you are trying to conceive and your temperatures are not doing what you expected, talk to your doctor.
  • Every woman's body is different, it may take more than one cycle to figure out what your patterns are.
  • Make sure you are consistent with measuring every day. If you do something out of the ordinary (i.e. are very stressed or have had too much alcohol), make a note of that day as an outlier so it does not mess up your measurements, but still record it.


  • Charting alone is not accurate enough to prevent pregnancy.

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Categories: Reproductive Health