The world has 307 million lakes, according to calculations made by an international team of scientists. That number includes all natural lakes, but not human-made lakes such as reservoirs formed by dams.
The lake count takes in ponds as small as one-tenth of a hectare (one-quarter acre). In fact, most lakes on earth are small, with nine out of ten lakes covering less than one hectare (2.5 acres).
The world's largest lake is the Caspian Sea, which extends over 378,119 square kilometres (145,993 square miles), an area about the size of Montana or Germany. The Caspian Sea is in a league of its own as no other lake tops 100,000 square kilometres in area.
Altogether, these natural bodies of freshwater cover 4.2 million square kilometres (1.62 million square miles) of the earth's surface. That's an area equivalent to more than half the size of the contiguous United States and makes up 2.8 percent of the earth's continents.