Montana is about 1.2 times smaller than Papua New Guinea.

Papua New Guinea is approximately 462,840 sq km, while Montana is approximately 376,979 sq km, making Montana 81.45% the size of Papua New Guinea. Meanwhile, the population of Papua New Guinea is ~9.6 million people (8.6 million fewer people live in Montana).
Tip: This to-scale comparison of Papua New Guinea vs. Montana uses the Mercator projection, which distorts the size of regions near the poles.
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