Detroit is about 26 times bigger than Cocos (Keeling) Islands.

Cocos (Keeling) Islands is approximately 14 sq km, while Detroit is approximately 359 sq km, making Detroit 2,466% larger than Cocos (Keeling) Islands.
Tip: This to-scale comparison of Cocos (Keeling) Islands vs. Detroit uses the Mercator projection, which distorts the size of regions near the poles.