I use ova but they all give a general idea until u enter ur data a few months to become accurate. once I tested for ovulation a month or two my app has become super accurate based on the data I entered from the strips and symptoms. For example most women ovulate about 2 weeks after ur period but I ovulated just over a week ovr so my fertile week as off on both glow and my ovia app until I took the tests and entered my data now it shows correctly when my window is. The app can't know for sure but just makes an educated guess until u give it something more to go off of.

Fertility Friend