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Identifying ovulation with BBT charting

For many women, the most obvious part of the menstrual cycle is just that - menstruation! In the work I do as a fertility awareness educator, I teach women to become aware and in tune with their entire cycle, beyond just menstruation. However, there is a cascade of hormonal events going on in between your period, and those events hinge on one thing: ovulation.

Important note: Reading this blog post is just an overview of the rules of basal body temperature shifts, please consult an instructor or learn a method completely before relying on a method of fertility awareness for birth control.

"Ovulation is a one-time event that allows the possibility of conception to occur."

Each and every day, our bodies are giving us important messages about our cycle and our health, and it is up to us to pay attention and listen. By charting our cycle we learn to listen to our body and interpret its messages and signals.

How to chart your cycle?

There are a number of different tools to track and chart our cycle. Some can tell us that ovulation is approaching, and others tell us that ovulation has already happened.

Before choosing the tool or method that works for you, it's important that you define what are you using charting for. If you are using BBT charting to avoid pregnancy than knowing that ovulation has occurred is probably what you are looking for. However, if you are trying to conceive knowing that ovulation is approaching will help you identify your fertility window and help you get pregnant faster.

Nevertheless, it’s important to note that we can never know definitively when ovulation is going to occur, we can only know for certain that it’s happened after the fact. 

Basal Body Temperature

Our basal body temperature is the body’s lowest temperature attained during rest. Our temperatures before ovulation are within a certain range. After ovulation, the presence of progesterone causes our basal body temperature to rise very slightly (about .1°C/.2°F). This slight rise is identified by daily tracking of our basal body temperature. 

In order to get as accurate as possible temps using a basal body thermometer, you will need to take your temperature daily at the same time each morning, before getting out of bed.

Alternatively, you can choose  Tempdrop, which takes your temperature throughout the night so there is no need to wake up and temp! and you get accurate readings regardless of how many times you woke up during the night or when you woke up.


BBT Charting

Sample chart: Pre and Post ovulation temperature readings.

Once ovulation occurs, your temperature will rise shortly thereafter. In order to confirm ovulation, you will need to wait for 3 consecutive days of readings indicating a rise in your temperature.

Choosing a set of rules to follow for BBT charting is important to be able to identify a temperature shift and ovulation.

There are two main methods of marking a temperature shift, the rules from the book "Taking Charge of Your Fertility" by Toni Weschler, and the rules for the Sensiplan method of Symptothermal fertility awareness, which are published in English by Reply Obgyn.  

The Sensiplan Method of Symptothermal fertility awareness

A regular shift with Sensiplan is considered to be one higher temperature above the previous six days, followed by at least 2 additional higher temperatures. A cover-line is drawn through the highest of the prior 6 temperatures to help you visualize this shift. The third day of your shift must be at least .2°C/.4°F above the cover-line. 

Sample chart: Sensiplan Method with cover-line.

Since not everyone will experience a regular shift in temperature, the Sensiplan system includes sets of rules that are designed for women who don’t meet the regular shift rules.

Fertility Awareness Method

The fertility awareness method for observing ovulation requires pairing basal body temperature with another indication of ovulation. There are many options and it depends on the method of fertility awareness that you choose.

A common pairing used by women is cervical mucus together with basal body temperature, which is used in the symptothermal method of fertility awareness. By using two indicators you can get a more accurate understanding of your cycle and of ovulation. Other markers of ovulation will either help you know when ovulation is approaching or will assist in confirming ovulation.

Understanding your body’s cues with basal body temperature allows you to understand your health and know whether you’re ovulating or not.

This information is valuable if you are looking to avoid pregnancy or get pregnant as well as for understanding the changes your body goes through and taking better care of your health.


For more information on using fertility awareness-based methods, check out Tempdrop’s free guide to fertility awareness written by fertility awareness educators.

Nathalie Daudet is a social worker and FEMM instructor based in Winnipeg, Canada. She discovered fertility awareness after searching high and low for a non-hormonal method of birth control. After learning the magic of fertility awareness and the gift of body literacy, she decided to pursue formal fertility awareness training and share the knowledge of fertility awareness with women looking for a natural birth control option. Fertility Awareness Project is the hub for Nathalie’s FEMM classes in both group and individual formats, online and in-person in Winnipeg. If you love this post and would like to thank Nathalie, shop Tempdrop with Nathalie's unique referral link