Heard Island and McDonald Islands is about 351 times smaller than Iowa.

Iowa is approximately 144,701 sq km, while Heard Island and McDonald Islands is approximately 412 sq km, making Heard Island and McDonald Islands 0.28% the size of Iowa.
Tip: This to-scale comparison of Iowa vs. Heard Island and McDonald Islands uses the Mercator projection, which distorts the size of regions near the poles.
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