I need to know how to retrieve the radius of the viewable zoom level in google maps API v3.
For example, if I am at zoom level 3, and depending on the users screen size (lets just say 400x400 viewable region) how do I get the "radius" circle of the viewable area.
Alternatively I'm currently using map.fitBounds() for all the points I've added to the map so really all I NEED is the radius of all the bounds. What I want is something like "20 miles" that I can feed into my database app.