Missoula is about 1.3 times smaller than San Francisco.

San Francisco (including the city proper only) is approximately 121 sq km, while Missoula (map shows its 17 named neighbourhoods; the area covers the whole city) is approximately 91 sq km, making Missoula 74.98% the size of San Francisco.
Tip: This to-scale comparison of San Francisco vs. Missoula uses the Mercator projection, which distorts the size of regions near the poles.
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