Chicago is about 2.8 times smaller than Johannesburg.

Johannesburg is approximately 1,644 sq km, while Chicago is approximately 590 sq km, making Chicago 35.88% the size of Johannesburg.
Tip: This to-scale comparison of Johannesburg vs. Chicago 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.