Kansas City is about 2.1 times bigger than Birmingham.

Birmingham (map shows its 87 named neighbourhoods; the area covers the whole city) is approximately 381 sq km, while Kansas City (map shows its 145 named neighbourhoods; the area covers the whole city) is approximately 815 sq km, making Kansas City 114% larger than Birmingham.
Tip: This to-scale comparison of Birmingham vs. Kansas City uses the Mercator projection, which distorts the size of regions near the poles.
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