Ulm is about 5 times smaller than Chicago.

Chicago is approximately 590 sq km, while Ulm (map shows its 55 named neighbourhoods; the area covers the whole city) is approximately 119 sq km, making Ulm 20.12% the size of Chicago.
Tip: This to-scale comparison of Chicago vs. Ulm 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.