I use 5,... well only 3 fertility predictor ones (this, ovia, and fertility friend) as well as kindara that doesn't predict and my regular <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> that ive used for years and does a basic prediction based on timing only.

I am wondering if anyone else gets wildly different predictions. Glow gives me a week long fertile window starting tomorrow... ovia says 5 days starting next tuesday, and ff says 4 days starting today.

Glow was pretty accurate last month, but wow... so confusing.