An akshauhini was an Indian
military unit formed from a particular ratio. The ratio is as follows:
A single akshauhini consisted of 21,870 chariots, the same number of elephants, 65,610 horse-mounted warriors and 109,350 infantry. The Kaurava army had 11 akshauhinis, the Pandava army consisted of 7.
In addition to the basic ratio of the unit each akshauhini had a number of scouts and medics.
It is said that during the Fourteenth Day's Battle Arjuna had to get from one end of the battlefield to the other in order to kill Jayatradha. He had from sunrise until sunset to cross a battlefield that raged with 18 akshauhinis and kill his enemy, or accept death himself.