Answer:
In New York City, approximately 17 to 20 street blocks equal a mile, and 5 to 10 avenue blocks equal a mile.
The length of the avenue blocks varies by neighborhood. Generally speaking, the avenue blocks on the West Side are long and the avenue blocks on the East Side are short.
Below 14th Street, though, these estimations cease to apply. Lower Manhattan is the oldest part of Manhattan, and its streets were mostly laid out before the city started expanding and the city planners decided to arrange it on a grid system.