Discover your menstrual cycle - and your fertility!

Daysy supports you in empowered and informed decision-making.

Buy Daysy

$320 or 4 payments of $80



Fertile / Possibly Fertile


Flashing Red

Predicted Day of Ovulation



Infertile Days



Learning Phase/Cycle Fluctuation


Red, Green & Yellow

Possible Pregnancy

What Daysy Does


There are only a handful of days each cycle that you are fertile. Daysy uses the Fertility Tracker Method (FTM) to calculate your fertile days and predict your ovulation. Daysy is programmed with a complex algorithm which evaluates your cycle by tracking your morning temperature (taken under the tongue) and knowing when you have your period. Daysy will then show you right away if you are currently fertile or not.

Why you can rely on Daysy


Daysy is German-made, Swiss-designed, with the foundation of over 3 decades of pioneering research, innovation, and experience from our family-run company. Based on 5 million menstrual cycles and knowledge from more than 30 years of research Daysy calculates the infertile days with an accuracy of more than 99%*.

* The independently reviewed result shows that Daysy has an overall accuracy of 99.4% in the calculation of infertile (green) days.


How to use Daysy

As easy as 1, 2, 3 ...


Every morning when you wake up, you measure your temperature under your tongue.

Daysy uses a proven algorithm and the morning measurement of your basal body temperature to calculate the daily menstrual cycle status in real time.


Enter if you have your menstruation.

Confirm you are menstruating for each day of active bleeding and flow for a minimum of three consecutive days


Daysy evaluates your data and shows you if you are fertile or not.

In addition, Daysy records your menstrual cycle and ovulation history and DaysyDay displays your past and present cycle data. It is hardly easier to become aware of your body.