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Home > Technical questions about OvuSense Sensor and App > How does OvuSense calculate ovulation?

How does OvuSense calculate ovulation?

Over a number of years, clinical studies have identified that a sustained rise in temperature is associated with ovulation.    OvuSense builds on this original clinical work with a set of new methods which predict (1) and confirm (2) the date of your ovulation in each cycle.   OvuSense is specifically looking for a sustained rise in your average core temperature.  In general, an increase of at least 0.3 degrees Celsius over three days indicates ovulation though your pattern may vary.

  1. If OvuSense sees two or three days where the temperature has risen in a particular pattern it will put a green shaded 'ovulation window' on your chart.    The ovulation window starts one day before ovulation and continues until two days after ovulation.   At the same time it will tell you that your expected ovulation date is 'tomorrow' or 'today', or it may just say that 'you are now in your ovulation window'.   
  2. OvuSense checks whether the rise is sustained and then confirms the date on which you ovulated.   This happens 3-4 days after ovulation occurs.  

As your cycle progresses, OvuSense will continue to update this information.   As a result, OvuSense may move the ovulation window.  Or it may decide that the rise no longer looks like ovulation at which point it will state 'ovulation not confirmed' and the green ovulation window will disappear.  If this happens, don't worry, just keep using OvuSense as ovulation may be confirmed later in the cycle. As long as you act on the information OvuSense provides and have sex as often as you can around the ovulation window, you will be maximizing your chances of getting pregnant.   

OvuSense Tips: 

  • Your temperature is likely to vary a lot from day to day.  That's normal so don't worry - it's the overall pattern in the cycle that's important. 
  • The pattern you see in your graph is not exactly the same as the one OvuSense uses for calculating ovulation - that's because it averages the data it receives over time.
  • Once you get to know your cycle with OvuSense, you should be able to see the start of the ovulation pattern before OvuSense provides a prediction.  
  • OvuSense is likely to produce different results from other temperature based methods and fertility Apps if you are using those at the same time.  


How reliable are the results?

  • OvuSense is cautious about providing predictions (1), and will show you one or more of the prediction messages in about 95% of cycles.  When it shows the ovulation window, clinical studies have proven OvuSense gets it right 92% of the time.
  • Clinical studies have shown OvuSense will confirm ovulation (2) in 99% of the cycles where an ovulation happens, and with a proven accuracy of 99%.

What is the clinical proof?

  • The rise in temperature to detect ovulation was identified in a clinical paper by Barrett and Marshall (1969) and developed further by McCarthy and Rockette (1983).   
  • The results of the trials detailing the OvuSense methods were published in Papaioannou et al. (2012a, 2012b, 2013, 2014).