Western Sahara is about 1.2 times smaller than Vietnam.

Vietnam is approximately 331,210 sq km, while Western Sahara is approximately 266,000 sq km, making Western Sahara 80.31% the size of Vietnam. Meanwhile, the population of Vietnam is ~101.6 million people (101.0 million fewer people live in Western Sahara).
Tip: This to-scale comparison of Vietnam vs. Western Sahara uses the Mercator projection, which distorts the size of regions near the poles.
Our free app, MapSize by MyLifeElsewhere — compare any two places, to scale on your mobile device.