Bronx is about 3.8 times smaller than Vienna.

Vienna is approximately 415 sq km, while Bronx is approximately 109 sq km, making Bronx 26.34% the size of Vienna.
Tip: This to-scale comparison of Vienna vs. Bronx uses the Mercator projection, which distorts the size of regions near the poles.
Our free app, MapSize by MyLifeElsewhere — compare any two places, to scale on your mobile device.