How long does my iPhone need to be on for find my iPhone to work?

Ok so i lost my iPhone sunday and I'm wondering how long the phone needs to be on for the app find my iPhone can find it? Like is it spontaneous? Does it take a minute?

Be sure to put it in lost mode. I would also put the permanent msg on the screen saying somehting like "This is stolen, please email me at xxxxxx". Sometimes people find them and don't know how to contact the owner.

It will usually check in within a couple of minutes once it is turned on.

Explain in more detail please.

It only takes a few minutes max. Here's two big problems. Are you sure you had Find my iPhone installed? Did you (un)install the radar screen looking app? Do you have an iCloud account? If you don't then give up. No way to fix that. Also, you lost it? What was the battery life when you lost it? It has to have power to ping a signal. If it's dead or a thief cut it off, this will not work either. Best luck.