The Google Distance Matrix API allows creating shipping rules that are based on actual distance/radius using real data from Google’s databases.  Add-on settings include “Units” as Miles or Kilometers, and “Distance Basis” as Driving, Walking, or Bicycling.

With this add-on, you will be able to create shipping rules with Minimum/Maximum Distance, as well as charge per Mile/Km, and even set a Table rate that is based on Miles/Km.