Oman is around the same size as New Mexico.

New Mexico is approximately 314,310 sq km, while Oman is approximately 309,500 sq km, making Oman 98.47% the size of New Mexico. Meanwhile, the population of New Mexico is ~2.1 million people (1.7 million more people live in Oman).
Tip: This to-scale comparison of New Mexico vs. Oman uses the Mercator projection, which distorts the size of regions near the poles.