Idaho is about 1.3 times smaller than Nevada.

Nevada is approximately 284,448 sq km, while Idaho is approximately 214,314 sq km, making Idaho 75.34% the size of Nevada. Meanwhile, the population of Nevada is ~2.7 million people (1.1 million fewer people live in Idaho).
Tip: This to-scale comparison of Nevada vs. Idaho uses the Mercator projection, which distorts the size of regions near the poles.