Of the 9,000,000 km2 of desert land in the Sahara, an area of about 2,800,000 km2 (about 31% of the total area) receives an annual average rainfall amount of 10 mm (0.39 in) or less, while some 1,500,000 km2 (about 17% of the total area) receive an average of 5 mm or less.