New York City is around the same size as Singapore.

Singapore is approximately 719 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 9% larger than Singapore.
Tip: This to-scale comparison of Singapore vs. New York City uses the Mercator projection, which distorts the size of regions near the poles.