Cities 101: The Algorithm for Finding the Nearest Cross Street for Manhattan Addresses in NYC

Imagine this: You walk out of Port Authority after a long bus trip, and need to find your best friend’s apartment at 383 Madison Avenue. As you take your phone out of your pocket, a commuter with no patience for dawdlers rushes past you, bumping your arm, causing your phone to fall and smash into smithereens on the sidewalk. So what do you do? Luckily, there’s a mathematical formula that will help you estimate the cross street of any address in Manhattan, and all it requires is a bit of mental math.

First, drop the last number of the address (in your friend’s case, 383 Madison Avenue would become 38). Divide that number by 2 (19). Then, you must add or subtract to that number according to the number corresponding to the avenue, provided by the chart below (19 + 26 = 45). 45th Street is one of the cross streets of 383 Madison Avenue. This address system has been around a long time, but it’s rather cumbersome to have to bring a copy of the key

Professor Ben Wellington from Pratt Institute took this subject a bit further on his blog I Quant NY and mapped out the entire address system in Manhattan using information from the NYC Open Data portal. The darker the area on the map, the higher the address number.
Map via I Quant New York 

In some of Wellington’s conclusions he finds that the street with the highest number is not surprisingly Broadway (#5365), the longest street on Manhattan:

The avenues on the Upper West Side change names, from numbers to names like Columbus Avenue, Amsterdam Avenue, etc. which explains the sudden lightening of colors at 59th Street:

Those behind the development of the 1811 Commissioner’s Grid which planned out the 11 major avenues and 155 crosstown streets that provided the foundation for the city grid we know today must have known about, or perhaps even devised, this formula. To learn more about New York City’s 1811 original map, check out our 14 Fun Facts About the Original 1811 Commissioners’ Plan for NYC.