The amount of city blocks in a mile is greatly dependent upon the city, since there is no universal standard for city block sizes. In some cities that use rectangular grids, the answer would also be dependent upon whether blocks are traversed along their length or their width.
Most cities blocks are square grids, meaning that their length and width measurements are the same. In this case, it would only be necessary to know the number of feet on which the grid is based. City blocks can range from 200 all the way to 900 feet on one side. There are 5,280 feet in a mile. So to find out how many city blocks would equal a mile, simply divide 5,280 feet by the number of feet in a block in any given city. In Tucson, Ariz., for example, blocks are 400 feet long. So 13.2 blocks would equal 1 mile.