BBT Chart


Every menstrual cycle, a woman’s body temperature will fluctuate, signifying the moment of ovulation. Specifically, a drop in the body temperature can be noticed at the beginning of a menstrual cycle and then a slight increase at the beginning of ovulation. By taking a note of the change in temperature, using a process called charting; women are better able to determine when ovulation has occurred.

The process of charting your temperature is based on the basal body temperature (BBT), which is a measure of the temperature at complete rest. There is no absolute standard of basal body temperature, but it generally ranges from 96 degrees to 98 degrees when taken with an oral thermometer.  When ovulating, this raises to a range of 97 to 99 degrees.  The challenge with charting basal body temperature is that the change in temperature may be very small. It is not uncommon for it to be as little as 1/10 of a degree. In order to ensure the best results, use a larger scale basal thermometer that only reads temperatures between 96 and 100 degrees.


Optimal Ways to Take Your Temperature

The basal body temperature should be taken prior to any activity. This means record your temperature before you eat, drink, have intercourse or even get out the bed for any reason. It is also a good idea to complete the process at the same time daily. If this is a challenge, use an alarm clock that will remind you to take your temperature. Prior to using a basal thermometer, read all of the instructions so that you get an accurate reading.  Web MD suggests that your temperature should be recorded to the closest 1/10th of the degree and written onto a basal body temperature chart. If your thermometer does not include one, there are many charts available online.

Recording Your BBT on a Chart

In order to show a pattern, every single reading that you complete must be written onto the chart. Once you have collected enough readings, you should be able to notice a pattern. You may see changes in your temperature that are sudden, occur in steps, or is even quite gradual. It is not uncommon for the patterns to vary with each is cycle.

Variation in your basal body temperature will occur because a number of factors can influence it. Physical stress, emotional distress, or even lack of sleep, will cause the temperature to perform outside of a typical pattern. Simple changes in environment such as disturbed sleep, alcohol consumption, illness, or even using an electric blanket, should be taken into account when keeping track of your basal body temperature. Record these events on your chart so that you can better understand your reading.

Web MD also mentions that if you are new to charting, it is a good idea to seek the advice of a medical specialist. Fertility professionals such as doctors, nurses and family planning professionals can help you with completing your chart. Although you should not need their help long term, their assistance can help you develop the skills you need to continue it long term. It is recommended that BBT charts are recorded for at least three months before they can be considered a reliable family planning method.

One thing to keep in mind about basal body temperature charting is that while accurate in determining when ovulation may have occurred, it cannot determine when it will happen in the future. That is why keeping several months worth of charts is very important to determine a potential pattern. When the pattern has been realized, it makes it easier to determine the best time to engage in intercourse that will lead to conception.

Intercourse that occurs within a few days prior to ovulation has a good chance of successfully fertilizing its egg. This is because sperm typically retain their fertilizing ability for up to three days, but some can last for five. If you have charted your potential ovulation date correctly and within a few days, you have increased the possibility that his sperm will be able to fertilize your egg. Additionally, combining BBT charting with other fertility tracking methods can help calculate ovulation ahead of time.