OvuSense logo

How to Use BBT to Track Ovulation

If you’re trying to track when you ovulate – and there are plenty of reasons you might want to do this, not just to boost your chances of getting pregnant – one of the most reliable things you can do is use your BBT. It’s not always easy to get however, and nor is it straightforward to understand the results.

OvuSense is here to help: we can help you understand what BBT monitoring is and whether it should form an important part of your fertility planning.

What is BBT?

BBT stands for ‘Basal Body Temperature’, and it is, as it sounds, the basic minimum temperature of your body.

While you’re awake, moving around and needing energy (not just for physical actions like heavy lifting, but even passive things like keeping your body warm or even simply thinking) your metabolism provides that energy, with the side effect of heat. Every action you take heats your body’s core temperature. When you rest for an extended period – in a full night’s sleep, your metabolism slows, your heartrate drops and your temperature drops. It’s such a routine for your body that you actually help yourself sleep by having a hot shower before bed! As you step out of the warm shower cubicle into the cold air, your body temperature drops and this tells your brain it’s time for bed, so you feel drowsy and find it easier to drift off.

This low, minimum temperature is affected by your menstrual cycle: and by measuring it every day of your cycle across multiple cycles you can reveal a pattern than tells you when you’re due to ovulate.

How to Measure BBT?

To get the most accurate readings, you’ll need to take your temperature first thing in the morning, when you first wake up. You should keep a thermometer at your bedside so you can take a reading without having to get up and fetch it, boosting your temperature, and obscuring the small changes you’re looking for.

Most BBT monitors use oral thermometers to measure your temperature, however this is limited in it's accuracy as they tend to only be capable of giving a reading to the nearest tenth of a degree. This can miss very slight alterations in your body temperature that may have an impact on the accuracy of your overall ovulation prediction.

Tracking and Understanding

You’ll need to take a reading every day, for multiple cycles to start to understand your personal pattern. This can prove time-consuming and difficult for people to maintain over an extended period of time, and even if you are vigilant in your record-keeping, using previous month's data to predict your current cycle can prove insufficient for those with irregular cycles or fertility issues such as PCOS (Polycystic Ovary Syndrome).

What you’re looking for is a deviation from the average, whatever your average is. Before ovulation, your core temperature is normally between 36.1C and 36.4C, and after you should see it rise quickly to between 36.4C and 37C. Many women also notice a sudden drop before ovulation, which is good indicator that it’s about to occur.


OvuSense can make all of this much more simple. Our vaginal sensor solves the issues associated with oral thermometers by recording the true fluctuations of progesterone throughout your cycle, to ensure you have the best and most accurate readings. Our companion app is backed by an algorithm that turns this data into a more accurate ovulation prediction that is clinically proven to be correct 96% of the time, and with 24 hours advance notice!

Find out more about core temperature technology and fertility here