Daysy – your personal fertility calculator

With fertility calculator Daysy you now have the choice!

Daysy is an intelligent fertility calculator that helps you to get to know your menstrual cycle and body better. But what exactly does Daysy have to offer?

Based on measured data from your unique cycle, Daysy tells you on which days you can  and on which days you cannot.

Daysy calculates your fertile window - with an from day one! Your fertility status will be displayed either as a red (you are fertile) or green (you are not fertile) light.


As easy as 1, 2, 3...

Only 30 seconds per day!

Achieve a higher awareness of your body with Daysy: In just 3 steps and within 30 seconds a day!

  1. Every morning when you wake up, you measure your temperature under your tongue.
  2. Enter if you have your menstruation.
  3. Daysy evaluates your data for the next 24 hours and shows you if you are fertile or not.


"I would absolutely recommend daysy. I am very conscious of what I put into my body, so when I started researching the pill I knew it wasn't the form of birth control I wanted to use, and I wanted to use a natural form of birth control and trust my body. I thought tracking my cycle would be complicated, but Daysy makes it so easy! Right now, I'm not planning for a baby but I know Daysy will be just as helpful in that stage of life as Daysy is right now."

Brooke, Preschool teacher

"I recommend Daysy to everyone. She and I are good friends. Switching to using Daysy instead of the pill or other hormonal birth control was the best decision I ever made. It helped eliminate the need for not only the pill, but it also helped reduce the postpartum depression I was suffering from, and allowed me to ween off my medication as well. Being in touch with my body is such a wonderful feeling and I feel much more in control of not only my fertility but also my life."

Amanda, Stay at Home Mom

"Daysy allows me to take control of my cycle without hormones or side effects. I can use Daysy and not have to worry about making errors the way I would with the calendar or mucus method alone. I can be confident that I am understanding my body well and being responsible with my future!"

Anonymous, high school math teacher:

"I would absolutely recommend it. I love daysy and how easy it is to use, plus the tracking makes it simple to show my doctor how things are going. My husband and I are both very concerned about the effects of hormonal birth control, but don't want to throw caution to the wind. Daysy makes it easy for us to monitor fertility together, without all the side effects of HBC."

Lauren Halcik, HR Director

USD 330.00

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You can count on Daysy!

Why is Daysy so reliable? The fact that Daysy can determine your fertile days with an accuracy of 99.4 % is due to the extensive database. Based on 5 million menstrual cycles and an algorithm that draws on knowledge from more than 30 years of research including clinical studies, Daysy can thus gives you reliable information about your menstrual cycle.

  • Red = fertile
    On red days, you can plan a baby.

  • Red flashing = day of ovulation
  • Green = infertile
    You are not fertile on green days.
  • Yellow = learning phase/cycle variations
    On yellow days, Daysy becomes better acquainted with you. If pregnancy is out of the question for you right now, consider these days red.

You can start with Daysy on any day of your cycle. Our customers appreciate the fact that measurement and fertility display can also be used independently of smartphone integration. Connecting to your smartphone is relevant for details and special features, e.g. if you want to display your menstrual cycle history or share it with your partner or doctor.

The algorithm of Daysy, which is also used by the well-known Lady-Comp fertility calculator of the sister company, has proven its safety for more than 3 decades. You will notice how exciting it is to get to know your body better with Daysy!


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Keep track of everything with the Daysy app.

Simply connect your Daysy cycle computer to the app DaysyView to see all your menstrual data at a glance.

Once you have connected Daysy to the app, the cycle computer will automatically synchronize your data with DaysyView.

DaysyView shows you your individual menstrual cycle calendar, your temperature curve and gives you a prognosis for the coming days and weeks.

Via the app, you can also share your cycle details with your partner or doctor.

Discover DaysyView!

  • Check out your daily fertility.
  • Check your weekly fertility status.
  • View your colorful monthly calendar.
  • Take notes.
  • Look at your predicted menstrual cycle curve.
  • Look at your temperature curve.
  • Check your menstrual cycle statistics.
  • Partner app – share your menstrual cycle data with your partner.
  • Enter when you had sexual intercourse.
  • Receive notifications when your menstrual cycle changes.
  • Contact our expert team if you need advice and support.
  • Receive free cycle analyses.

Medical basics related to the female cycle


Every woman is different,

but there are some basic physiological facts about the woman's menstrual cycle that you should know:

  • As a rule, 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 can be fertilized within 18 hours at the most.
  • 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.


How exactly does the Daysy fertility calculator work?

Daysy uses a morning measurement of your basal body temperature to detect ovulation in your cycle. Just measure the temperature under your tongue in the morning and you will know whether you are fertile or not. Depending on the current cycle phase, the indicator lights red or green.

In addition, Daysy records your menstrual cycle history and shows you which cycles are currently taking place in your uterus. It is hardly easier to become aware of your body.

What makes Daysy so special? This fertility computer has no side effects: no hormones, no risk of thrombosis, or other side effects. There is no better way!

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