San Francisco is about 32 times smaller than Melbourne.

Melbourne (the 27 councils of metropolitan Melbourne, without the Yarra Ranges, Cardinia, Mornington Peninsula and Nillumbik) is approximately 3,915 sq km, while San Francisco (including the city proper only) is approximately 121 sq km, making San Francisco 3.09% the size of Melbourne.
Tip: This to-scale comparison of Melbourne vs. San Francisco uses the Mercator projection, which distorts the size of regions near the poles.
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