Antarctica is about 5.5 million square miles (14.2 million square kilometers) in size, making it the fifth-largest continent on Earth. It is roughly twice the size of Australia, nearly 40% larger than Europe, and about the same size as the combined areas of the continental United States and Mexico. Most of Antarctica is covered by thick ice, averaging about 1.9 km (1.2 miles) thick but reaching nearly 3 miles in some places. The continent also experiences large seasonal variations in size due to the extent of surrounding sea ice, which can expand its area significantly in winter.