What is the approximate area of the Sahara Desert in square kilometers (1 km² ≈ 0.39 sq mi)?

Answer

9,200,000 square kilometers

The Sahara is roughly the size of the entire United States. Just 6,000 years ago it was a green landscape of lakes and grasslands, dotted with hippos and human settlements.

Source: Wikipedia (widely cited figure; Britannica gives ~8.6 million km²)