Starting at 1st level, a barbarian can rage for a number of rounds per day equal to 4 + her Constitution modifier. At each level after 1st, she can rage for 2 additional rounds. Temporary increases to Constitution, such as those gained from rage and spells like bear's endurance, do not increase the total number of rounds that a barbarian can rage per day. A barbarian can enter rage as a free action.
4 + Con + (2 pro barb LVL nach dem Ersten)