I am working on an Android app which makes use of geofence. I want user to decide the radius of geofence. But I want to know what is the minimum and maximum radius for the geofence so that app will work fine.
For best results, the minimum radius of the geofence should be set between 100 - 150 meters.
=> When Wi-Fi is available location accuracy is usually between 20 - 50 meters.
=> When indoor location is available, the accuracy range can be as small as 5 meters. Unless you know indoor location is available inside the geofence, assume that Wi-Fi location accuracy is about 50 meters.
Check and read developer site
https://developer.android.com/training/location/geofencing.html
You can set 50-100 meters as minimum for all conditions.