Western Sahara is about 13 times bigger than Massachusetts.

Massachusetts is approximately 20,306 sq km, while Western Sahara is approximately 266,000 sq km, making Western Sahara 1,210% larger than Massachusetts. Meanwhile, the population of Massachusetts is ~6.5 million people (5.9 million fewer people live in Western Sahara).
Tip: This to-scale comparison of Massachusetts vs. Western Sahara uses the Mercator projection, which distorts the size of regions near the poles.