Seoul is about 1.3 times smaller than New York City.

New York City (including all five boroughs: Manhattan, Brooklyn, Queens, The Bronx, and Staten Island) is approximately 781 sq km, while Seoul is approximately 605 sq km, making Seoul 77.5% the size of New York City.
Tip: This to-scale comparison of New York City vs. Seoul uses the Mercator projection, which distorts the size of regions near the poles.
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