Fort Lauderdale is about 3.9 times smaller than Atlanta.

Atlanta is approximately 350 sq km, while Fort Lauderdale (excluding the city's 9.9 sq km of water area) is approximately 90 sq km, making Fort Lauderdale 25.68% the size of Atlanta.
Tip: This to-scale comparison of Atlanta vs. Fort Lauderdale uses the Mercator projection, which distorts the size of regions near the poles.