Fort Lauderdale is about 4.8 times smaller than Montreal.

Montreal is approximately 432 sq km, while Fort Lauderdale (excluding the city's 9.9 sq km of water area) is approximately 90 sq km, making Fort Lauderdale 20.86% the size of Montreal.
Tip: This to-scale comparison of Montreal vs. Fort Lauderdale uses the Mercator projection, which distorts the size of regions near the poles.