Natural fertility tracking powered by you.

Daysy brings the inside out, translating your unique raw data so that you're in the know.

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

Power in Your Life - the Daysy Effect


Your body operates in rhythms and cycles and with Daysy in your hand, you'll understand your body better. Accurately predicting your menstruation and knowing the few monthly days when you are fertile. Supporting you to learn the signs and personality of each phase. A record of your personal health securely stored only in the Daysy device, the choice yours on sharing with a partner and or a medical professional.

Daysy - the Science


Daysy uses a highly accurate basal body temperature measure, to a thousanth of a decimal point (0.0324) to calculate individual hormone levels. It is founded on the Fertility Tracker Method (FTM). Using a single data point - you - combined with engineering innovation to spark the complex algorithm that evaluates and confirms your unique fertility status. Four options only: Fertile, not fertile, inconclusive or pregnant.

Depend on Daysy - the Facts


Generations of fertility expertise blended into a device and app. A family business. Swiss engineering fuelled by passion and led by a female visionary. It’s a partnership and we count on the strength of over 5 million menstrual cycles tracked and 500,000 contributors to date who have informed the accuracy and understanding of fertility. We thank you and wouldn't be here without you.


How to use your Daysy

Period Power in 3 Steps


Awake. Eyes open. Place under your tongue for up to 60 seconds. Listen for the beep.


Morning basal body temperature recorded within 0.0324 degrees Fahrenheit. Learn which phase you're in.


In minutes know if it's a red, yellow or green day. Red is fertile. Yellow is a learning phase or cycle fluctuation. Green is not fertile.