Grand Rapids is about 3.1 times smaller than Detroit.

Detroit (map shows its 92 named neighbourhoods; the area covers the whole city) is approximately 359 sq km, while Grand Rapids is approximately 116 sq km, making Grand Rapids 32.28% the size of Detroit.
Tip: This to-scale comparison of Detroit vs. Grand Rapids uses the Mercator projection, which distorts the size of regions near the poles.
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