When you are charting your temperature it is very important to draw a coverline. This coverline will allow you to determine when you have ovulated because it shows the shifts and surges in temperature. The coverline will also help you keep track of your temperatures after you have ovulated.

Drawing the Coverline

You draw your coverline when your waking body temperature, i.e. basal body temperature, has risen higher than 2/10s of a degree from the previous six days. Usually, this happens the day after ovulation during your thermal shift. Some women are confused about how much 2/10s of a degree is and an example would be if your temperature has been 97.7 the past six days and it rises to 97.9 then you have experience a 2/10s rise in temperature. Once you have reached the time when your temperature is 2/10s higher then you will need to highlight the six days prior to the temperature shift. Check the highlighted temperatures and note the highest one. Now, take a pen and draw a straight line that is 1/10s of a degree higher than your highest temperature on the chart. The line should run all the way across your sheet. So, if your highest temperature was 97.7 then you will draw your coverline at 97.8 because that is 1/10 of a degree higher.

Temperatures to Ignore

There are temperatures you will need to ignore. For example, if you have an out of the ordinary temperature reading that is really high, due to illness, stress, lack of sleep, or medication then you will want to overlook those temperatures. Don’t use high menstrual period temperatures in your coverline, either.


By charting your basal body temperature and having a coverline you will be able to tell when ovulation occurs. Usually, this will happen on day 15 and having intercourse after ovulation will not result in conception. That’s why it’s important to chart for a few months to see when you are most fertile so you know when to have intercourse if you are trying to conceive.