Do you also use a cycle app on your phone? Millions of women are already doing this and there are also more and more providers: After all, it is wonderful to be uncomplicated and cheap to prevent – or even faster to ensure that you get pregnant. Cycle Apps let you know on which days you can get pregnant at all. And depending on what the family planning looks like, then one has just sex (without further contraceptive method) or not. However, as a study by Stiftung Warentest shows, many apps are not very accurate. Especially if you use the method of contraception can have serious consequences. Most cycle apps are not really individual to the respective user, but simply work with the average cycle length, which, however, may differ greatly for some women. Or by stress, illness and other factors may additionally vary. And the actual time of ovulation is already in a completely different period than the app shows you. That's why 20 out of 23 apps failed the test (including Clue Menstruation & Cycle Calendar, WomanLog Pro Calendar and Flo Menstrual Calendar). 2 have finished with the grade "Good" (Lady Cycle and MyNFP), 1 still with "sufficient" (OvuView). The last three rely not only on pure mathematics, but also on the respective user who regularly has to measure her body temperature at the exact same time after waking up and daily has to observe the cervical mucus of the vagina. Combining all of this makes it possible to make a more reliable statement as to whether one would be fruitful or not. A "very good" was not awarded in principle, because for all Apps scientifically meaningful studies are missing.