New York City is about 184 times smaller than Illinois.

Illinois is approximately 143,961 sq km, while New York City (including all five boroughs: Manhattan, Brooklyn, Queens, The Bronx, and Staten Island) is approximately 781 sq km, making New York City 0.54% the size of Illinois.
Tip: This to-scale comparison of Illinois vs. New York City uses the Mercator projection, which distorts the size of regions near the poles.