Montana is about 139 times bigger than Rhode Island.

Rhode Island is approximately 2,706 sq km, while Montana is approximately 376,979 sq km, making Montana 13,831% larger than Rhode Island. Meanwhile, the population of Rhode Island is ~1.1 million people (63,152 fewer people live in Montana).
Tip: This to-scale comparison of Rhode Island vs. Montana uses the Mercator projection, which distorts the size of regions near the poles.