Chemnitz is about 1.8 times bigger than San Francisco.

San Francisco (including the city proper only) is approximately 121 sq km, while Chemnitz is approximately 221 sq km, making Chemnitz 83% larger than San Francisco.
Tip: This to-scale comparison of San Francisco vs. Chemnitz uses the Mercator projection, which distorts the size of regions near the poles.
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