A block is by no means a standard unit of measurement. Depending on the urban plan, blocks can be square or oblong, and can vary significantly in side length. For this plot, I measured the median length of downtown blocks in six cities that have regular grid layouts – that is, the dimensions of their city blocks are consistent. I’ve included blocks per mile along the outer axes, and the ratio of short to long dimension for each city. For this value, one represents a perfect square while smaller values indicate more oblong blocks.

Data source: Measurements made using Google Earth.