San Francisco is about 1.3 times bigger than Fort Lauderdale.

Fort Lauderdale (excluding the city's 9.9 sq km of water area) is approximately 90 sq km, while San Francisco (including the city proper only) is approximately 121 sq km, making San Francisco 34% larger than Fort Lauderdale.
Tip: This to-scale comparison of Fort Lauderdale vs. San Francisco uses the Mercator projection, which distorts the size of regions near the poles.