How to Chart Your Basal Body Temperature

by Caitlyn Stace

Basal Body Temperature Chart (Symptothermal Method)

A basal body thermometer (BBT) is an ultra-sensitive thermometer that tracks your body's exact temperature. A digital thermometer is your best bet. Each thermometer kit comes with a blank graph. These graphs may have space for you to record Pre-Menstrual Syndrome symptoms (PMS).

At the top of the graph are the days of your cycle from 1-40, but you add more days if you need to. Underneath each cycle day is the month and actual calendar date. Vertically listed are temperatures from 99.4-97.0 degrees F. In Canada, the readings would be in metric units, at from 37.4-36.1 degrees C.

Each morning, before you get out of bed, you'll need to take your temperature orally (you can vaginally, but orally is more accurate) and chart it on the graph. The graph will not be accurate unless you take your temperature the same time every morning.

After ovulation, your temperature rises between 0.36 and 0.9 degrees F (0.2 and 0.5 degrees C). After doing about three charts, you should notice a very distinct pattern of ovulation, which will help you time future intercourses and tell you whether you are ovulating regularly. However, this method will not tell you when to have intercourse, since the temperature does not rise until after ovulation. Do not make the mistake of planning intercourse around this chart. The purpose of the chart is to help you plan future intercourses and assist you in observing your own unique fertility pattern.

If you want to know ahead of time when you are ovulating, then this method is not for you. Ovulation kits and monitors are ideal for for pre-ovulation detection.

The next step is to have your doctor perform blood tests to check your hormonal levels, or do an endometrial biopsy, a test that determines whether you are ovulating or have a hormonal imbalance.

Guidelines for an Accurate BBT Chart

By charting your body temperature, it's simple to tell when pregnancy has occurred and when there is danger of miscarriage. Charting can allegedly help in choosing the sex of your baby by timing intercourse according to certain fertility signs.

Key Facts:

The first day of your menstrual flow is day one of your basal body temperature (BBT) chart. Do not include spotting prior to your period as day one. Your temperature should drop when your menstrual flow starts. Record your temperature throughout your period.

  1. Note the actual day of the month in the space provided on your chart.
  2. Use an oral, digital, basal body thermometer only. A regular thermometer will not work.
  3. Take your temperature each morning before you get out of bed. Place the thermometer under your tongue for at least 2-3 minutes.
  4. Don't eat or drink anything before you take your temperature.
  5. Record your temperature by using a dot, not an X or a check mark.
  6. Use a down-pointing arrow to indicate the days you had intercourse.
  7. Record any premenstrual symptoms if there is space on the chart. Otherwise, use your symptom chart to help link a certain temperature to a symptom.
  8. Note any special considerations like colds, illness or fever.
  9. Change charts when you get your period again.

Finally, on one of your charts, record what you are eating, how much you are exercising, and whether you are under any unusual stress. Coffee, alcohol, dieting, exercise, and emotional stress all affect your menstrual cycle in some way. Our tool lets you easily type in a note for that day. See our instructions here for more information on how to use's BBT Ovulation Charting Tool. Best of luck to you!

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