San Bernardino is about 1.3 times bigger than San Francisco.

San Francisco (including the city proper only) is approximately 121 sq km, while San Bernardino (map shows its 50 named neighbourhoods; the area covers the whole city) is approximately 161 sq km, making San Bernardino 33% larger than San Francisco.
Tip: This to-scale comparison of San Francisco vs. San Bernardino uses the Mercator projection, which distorts the size of regions near the poles.
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