Originally Posted by: qidashao28

I use an app on my phone to tune. What hz do I set it to to tune my classical guitar?

As jarkko mentioned the standard is A pitch at 440Hz. And there is no difference between classical guitar & any other style for the purpose of tuning.

One small point to correct, the open A string on the guitar is actually 110 Hz, 2 octaves lower than 440Hz.

https://en.wikipedia.org/wiki/Guitar_tunings

Hope this helps!