How accurate is share my location
It's going to vary, of course, but one way to get an approximation is to pull up the Maps app.

This article from Apple Support says the following about this...


  "Apps that can show your location on the screen, including Maps, show your current (approximate) location using a blue marker. If your location can't be determined precisely, you'll see a blue circle around the marker. The size of the circle shows how precisely your location can be determined—the smaller the circle, the greater the precision."


This article may be of assistance, too: http://n8henrie.com/2014/09/how-accurate-is-the-iphone-gps/