How Basal Body Temperature Works as an Ovulation Tracker

How Basal Body Temperature Works as an Ovulation Tracker


What is Basal Body Temperature?  

Basal Body Temperature (BBT) is your body's temperature at rest, and can only be accurately taken immediately when you wake up.
BBT rises after ovulation, due to increased Progesterone released from the corpus luteum after ovulation. Ovulation can be detected on a Basal body temperature chart for the day before the temperature rises. The number remains high if there is a pregnancy.
A Basal Body Temperature Chart example on the Premom App


An increase of 0.5-1¬ļF indicates the BBT spike, and occurs one-to-two days after ovulation. The purpose of BBT tracking and creating a BBT chart is to¬†find the temperature spike. Traditionally, women take their basal body temperature and manually mark the reading on a printed fertility chart or a note book. Then, they figure out the spike day after consecutive readings. The process to manually pinpoint your spike would take days of works and require a lot efforts.

A coverline is a horizontal line in your chart drawn directly above the last temperature before the spike (see the orange line in the graph above). The purpose of this is to separate preovulatory temperatures from postovulatory temperatures so that the BBT spike can be more evident: you will clearly be able to visualize the difference between the series of lower preovulatory temperatures underneath the coverline, and the series of higher postovulatory temperatures above the coverline.

Thanks to the rapid development of A.I. (Artificial Intelligence), you can sync your temperature readings on the Premom Ovulation Tracker app and find the coverline on your fertility chart.    

Why finding BBT spikes after ovulation can help me make predictions for fertile days?

This is because a normal woman’s Luteal Phase (the phase after ovulation day till the next period day) will always be the same number of days, not fluctuating by even one day.

Therefore, if you know both the length of your¬†Luteal Phase¬†‚Äď and when you will get your next period, from a proven, accurate menstrual cycle predictor ‚Äst your next¬†ovulation day¬†can be calculated.

A simple formula is as below:

- Your Next Period Day ‚Äď Luteal Phase Length = Next Ovulation Day

- Your Current Ovulation day + Luteal Phase Length = Your Next Period Day

Therefore, you can calculate when you will ovulate next if you know the number of days in your Luteal Phase, which is normally 11-17 days long, and if you know your next period day.  And you can calculate your next menstrual cycle start date if you know your Luteal Phase length and the ovulation day of your current cycle.  

Who should choose BBT tracking as an ovulation calculator?

The best-suited BBT tracking users are healthy, have a regular life schedule, and have a consistent wake up time. These women could choose a basal body temperature chart as an ovulation calculator.

We highly recommend the BBT tracking method to women who have PCOS, LUF, a short LH Surge, or low LH Surge levels, because these women can use a Basal Body Temperature chart paired with ovulation tests to confirm that ovulation has occurred.

What are challenges and solutions to BBT?

Challenges for different BBT tracking methods


How does BBT tracking works on the Premom app?

The Premom Ovulation Calculator app automatically syncs your basal body temperature after it is paired and connected with the Easy@Home basal thermometer.

Try free Premom ovulation tracker app

Premom can calculate ovulation regardless of the huge variety in BBT spike patterns because it has such an advanced algorithm in regards to fertility awareness.

The most challenging part of tracking basal body temperature is reading the chart and figuring out when the BBT spike occurs. However, the Premom app can automatically calculate and draw the coverline in the chart for users to see their own spike.

To get a coverline in the Premom app, there is some minimum criteria:

  1. The first six low consecutive temperatures must be lower than the next three higher consecutive temperatures (‚Äú6 low, 3 high‚ÄĚ).
  1. The gap between the highest of the previous six temperatures and the lowest of the next three temperatures is equal or greater than 0.5¬ļF (0.2¬ļC).

To have Premom show you the BBT spike and draw a coverline, you need to take at least 9 consecutive temperatures and record them in the app. You could either manually input the basal temperature from any basal thermometer you are using or you could use the Easy@Home digital basal thermometer, which syncs to Premom automatically through Bluetooth.

Without using Premom, many women have to take their basal temperature every day throughout their entire cycle, trying to find the spike out of all the temperature readings. After using Premom consistently, the app will understand your pattern better, and you can reduce the temperature-taking to the minimum while still catching your spike. 

When connected with the Easy@Home digital smart basal thermometer, BBT tracking can be as easy as 1, 2, 3!

1. Upon waking up, turn on the digital thermometer and put it under your tongue. Then relax!

2. When you hear the double beep after less than two minutes, it is done.

3. Your temperature is recorded and automatically syncs to your app tracker!  

Try Premom free ovulation tracker app