Reclaim your sexual health naturally and download the app Natural Cycles, designed to track your body’s temperature. The app will show your fertility for the day. A woman is fertile up to 6 days per cycle. The fertile window ends with the day of ovulation and begins up to 5 days before, depending on sperm survival. Natural Cycles carefully studies your body temperature to find your ovulation day and fertility. With over 15,000 users and a total of 420000 days on NaturalCycles there have been zero unwanted pregnancies.