San Francisco is about 16 times smaller than Jacksonville.

Jacksonville (map shows its 197 named neighbourhoods; the area covers the whole city) is approximately 1,935 sq km, while San Francisco (including the city proper only) is approximately 121 sq km, making San Francisco 6.25% the size of Jacksonville.
Tip: This to-scale comparison of Jacksonville vs. San Francisco uses the Mercator projection, which distorts the size of regions near the poles.
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