Generally, it is understood that the empire of the Mongols led by Genghis Khan was the largest in history. It was an enormous vast stretch of land that was claimed by the powers of the khanate, sultanate, kingdom, principality or empire taken over by Ghengis. These were absorbed into his kingdom through his lifetime. Considering the Roman empire is a different story altogether. Maybe it is true that the Roman empire did not have as much land conquered as the empire of Genghis Khan. But the influence of the Roman empire has impacted the whole world much beyond what anyone can imagine.
Their system of government and law has spread to many of the nations that still follow such systems even today. The spread of the Christian religion throughout the world in enormous ways also can be seen as an impact of the Roman influence as well. Finally, the cultural and philosophical impact is seen worldwide even to the modern cultures of today.
There are a lot of people who are aware that the Mongol Empire is also very large. They have started to wonder whether the Mongol Empire was bigger than the Roman Empire. The answer to this is no. The Roman Empire was bigger by over 1 million kilometers. It was able to reach more places during its peak.
It should be remembered that the Roman Empire became so large that they needed to divide it in order to keep track of the different areas that are part of the empire. This also became its weakness because its reach already became too big to manage properly. The Barbarians started to take over.
Genghis Khan ruled the Mongol Empire. It was considered to be a nomadic empire which means the people moved from place to place without settling down. Genghis Khan ruled the Mongol Empire from 1206 to 1227. He was the first ruler of this empire followed by five more until 1368.
The Mongol Empire was enormous and began with over four million kilometers in area. However, by the time Khan died, it reached thirteen million kilometers. Before the split, the Roman Empire was known to be very large. At its height in 117 AD, the Roman Empire reached five million kilometers. The Roman Empire was bigger than the Mongol Empire at one point which was in 117 AD. The population was about fifty-six million people in 25 BC.