Wyoming is about 1.2 times bigger than Idaho.

Idaho is approximately 214,314 sq km, while Wyoming is approximately 251,489 sq km, making Wyoming 17% larger than Idaho. Meanwhile, the population of Idaho is ~1.6 million people (1.0 million fewer people live in Wyoming).
Tip: This to-scale comparison of Idaho vs. Wyoming uses the Mercator projection, which distorts the size of regions near the poles.