Yellowstone National Park is about 1.2 times smaller than Big Island of Hawaii.

Big Island of Hawaii is approximately 10,434 km² (4,029 sq mi), while Yellowstone National Park is approximately 8,983 km² (3,469 sq mi), making Yellowstone National Park 86.1% the size of Big Island of Hawaii.
Tip: This to-scale comparison of Big Island of Hawaii vs. Yellowstone National Park uses the Mercator projection, which distorts the size of regions near the poles.

Compare further: Yellowstone National Park vs. Big Island of Hawaii

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