OSM data have no compilation scale information, so we (Chris Kempf, Pascal Neis, Max Rylov and Andreas Reimer) found an efficient way to calculate scale equivalencies for residential areas.
While the paper with the description of our linear-time method is under review, please do check out the visualized results!
http://openmapsurfer.uni-hd.de/scale-determinator.html
Note: the tile server for the results needs ~15 secs to “awaken”. The “New” result layer has incoprorated a hippodamian adjustment to catch and properly evaluate block based city grids fround from ancient Greece all the way to Manhattan and Australia.