1/3 of the schedule for most teams (without counting bowl games). The rule used to be you could redshirt if you got injured during the first 1/4 of the games on your schedule, so back in the day if a player blew out a knee in the first three games, he could redshirt. That was one reason why the Taysom season ending injury in 2014 sucked even worse. He got injured one quarter in to the 4th game (or was it the 5th game?). So no chance at a redshirt (if he even would have wanted it) unless he got a special approval.