Tucson is about 5 times bigger than San Francisco.

San Francisco (including the city proper only) is approximately 121 sq km, while Tucson (map shows its 130 named neighbourhoods; the area covers the whole city) is approximately 627 sq km, making Tucson 418% larger than San Francisco.
Tip: This to-scale comparison of San Francisco vs. Tucson 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.