San Francisco is about 5 times smaller than Tucson.

Tucson (map shows its 130 named neighbourhoods; the area covers the whole city) is approximately 627 sq km, while San Francisco (including the city proper only) is approximately 121 sq km, making San Francisco 19.29% the size of Tucson.
Tip: This to-scale comparison of Tucson vs. San Francisco 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.