Mobile location data in the US is accurate to about 30m

""PlaceIQ commissioned independent research from Findyr, a global technology company that provides brands with custom data and analyses, to conduct the study. The new study consisted of an independent, third-party analysis of more than 150 physical locations across five U.S. cities and found that on average, location data obtained via mobile smartphones is accurate up to 30 meters.
In addition, the average finding for location data accuracy varied in each of the five U.S. cities analyzed, which included Boston, MA (21 meters), New York City, NY (27 meters), Austin, TX (28 meters), Washington, D.C. (29 meters), and Chicago, IL (38 meters).
These findings are demonstrative of the complex relationship between multiple factors that affect location data accuracy, such as signal source (GPS signals, Wi-Fi, cell tower triangulation), environment (area density, skyline view, indoor or outdoor location), and personal use (location data access enabled, type of mobile app used, operating system usage)"

Source:  Yahoo, 25th May 2016