How large was the Mongol Empire at its greatest extent?

At its greatest extent, the Mongol Empire covered approximately 9 million square miles (23 million square km) of territory, establishing it as the largest contiguous land empire in world history.1

By the late 13th century, the empire stretched from the Pacific Ocean in the east to the Danube River and the shores of the Persian Gulf in the west. This vast domain was achieved through a highly effective military-bureaucratic system that unified the peoples of the Eurasian Steppe and conquered major regions, including all of China, most of the Middle East, and the majority of the Russian principalities.12