Montana is about 4.7 times bigger than Maine.

Maine is approximately 79,931 sq km, while Montana is approximately 376,979 sq km, making Montana 372% larger than Maine. Meanwhile, the population of Maine is ~1.3 million people (338,946 fewer people live in Montana).
Tip: This to-scale comparison of Maine vs. Montana uses the Mercator projection, which distorts the size of regions near the poles.