Kenya is about 1.5 times bigger than Montana.

Montana is approximately 376,979 sq km, while Kenya is approximately 580,367 sq km, making Kenya 54% larger than Montana. Meanwhile, the population of Montana is ~989,415 people (54.9 million more people live in Kenya).
Tip: This to-scale comparison of Montana vs. Kenya uses the Mercator projection, which distorts the size of regions near the poles.