How Daysy works

Safe and accurate from day one thanks to the Daysy fertility tracker

Calculating when you ovulate is no easy task. To be accurate, you need reliable data. Daysy makes it simple to know when you ovulate by taking your waking temperature, tracking this data, and calculating when you ovulate. Daysy indicates your fertile window with accuracy and safety.


These factors play a role in calculating your fertile days:

  • Cycle length: A cycle starts on the first day of menstruation (= 1st day of cycle) and ends on the day before the next menstruation. Each cycle is different and can even vary.
  • Your basal body temperature (waking temperature) is slightly lower in the first cycle phase and increases by 0.25-0.45°C around the time of ovulation.
  • Record all measurements and remember other factors that could have an influence, such as an infection or fever.
  • The subsequent calculation of your cycle.
  • Besides all the complicated things mentioned, do not forget to find the best time to be intimate with your partner.


Sounds like a lot of work? Well, it is! That is why we developed Daysy - so that you can calculate your fertile window more easily.

You do not have to do a lot of work: Just use Daysy in the morning to measure your basal body temperature under your tongue and enter if you have your period. Daysy automatically calculates everything for you. The compact ovulation tracker is easy to use and fast - but more importantly, Daysy is reliable.

If you use Daysy regularly, Daysy will not miss anything - on the contrary: Daysy records your cycle history so that you are always in the picture of what is happening in your body. Daysy offers a very safe and accurate ovulation calculation.

CHF 420.00

Daysy is a fertility tracker that uses the fertility awareness method by learning and tracking your menstrual cycle.

With Daysy you measure your body temperature (or: basal body temperature - BBT) in the morning with an advanced temperature sensor. Daysy then analyzes your measurement with the algorithm, which incorporates data from 5 million menstrual cycles and 30 years of research, and can tell you with certainty whether you are fertile or not.

The tried and tested Daysy program: With Daysy you can relax

The Daysy ovulation tracker recognizes, analyzes and displays your menstrual cycle individually and accurately. The technically supported temperature method is one of the safest methods in the world to determine fertility. Daysy has the same algorithm as that of the well-known fertility tracker Lady-Comp.

The Woman's Cycle: Medical basics

There are some basic physiological facts with regard to the cycle:

  • Every woman has only one ovulation per cycle.
  • If two or more instances of ovulation occur, they take place within 24 hours.
  • After ovulation, the ovum is fertile for a maximum of 18 hours.
  • Sperm is able to move and fertilize in a woman's body for a maximum of 5 days.


This means that pregnancy can occur on only 6 days, i.e. 5 days before ovulation and on the day of ovulation itself. Daysy calculates these 6 days and then indicates them to you along with buffer days on either side of that fertile window


Variations in the menstrual cycle: No cause for concern

Every woman has her own unique cycle, and it is not necessarily the same every month. Daysy learns your own cycle rhythm and how to assess it. At the same time, it gives you a sharpened awareness of your body.
Your cycle is influenced by your emotional state, too. Stress and other factors can also affect your body, which can have an impact on your cycle. By recording your data on a daily basis, Daysy is able to recognize and indicate these changes in your life.


CHF 420.00

Daysy is a fertility tracker that uses the fertility awareness method by learning and tracking your menstrual cycle.