For decades, the pill was the ultimate choice when it came to contraception. In the meantime, however, more and more women are turning away from it and preferring to use more natural methods instead of hormonal contraceptive methods. So-called cycle apps that are supposed to reliably predict which days a woman is fertile and which are not are currently in vogue. But unfortunately, many don’t do that. Stiftung Warentest tested 21 cycle apps, and the results are shocking. You can rely on just five applications.

More than half of cycle apps are based on math. Unfortunately, the human body is not as predictable as it needs to be for the applications to provide reliable forecasts. The cycle rhythm depends on many factors – including stress, diet and weight. Strength and cycle lengths can vary from month to month.

Anyone who calculates the fertile days according to the calendar or from the average values ​​of previous cycles can seriously be wrong “and become pregnant unexpectedly,” says Gunnar Schwan, who conducted the test. Warentest cannot therefore recommend cycle apps that work mathematically. Eleven apps failed the test with a “poor” rating.

Cycle apps work better, allowing women to measure their body temperature in the morning and also keep an eye on changes in their cervical mucus. This approach is called the symptothermal method. Both temperature and cervical mucus, which is produced in the cervix, change during the cycle. According to Warentest, the symptothermal method works “solidly” with some cycle apps – but not with all of them. The test showed that several apps were wrong in their prediction of fertile days, meaning that the method was not implemented correctly in the apps.

According to Warentest, none of the 21 cycle apps are great. The best ones are at least “satisfactory”. The test winners are the applications “Lady Cycle” and “MyNFP”. If the basic version is enough for you, “Lady Cycle” is even free – but only for Android users. Two of the most popular cycle apps are not recommended. Both “Flo” and the “Menstrual Calendar” provided such unreliable forecasts that the testers penalized them with a grade of 5.5.

You can read the complete product test for a fee on