"I'm not sure the exact percentage, I think 50 or something. A little bit over maybe," Smith said Wednesday of his injury.
The defensive tackle suffered the injury on Dec. 16 against the Patriots and missed the final two games of the regular season, ending his streak of 185 consecutive starts.
"I really haven't gone to the doctors yet. I figure I will do that after the Super Bowl," he said.
The 33-year-old Smith has nine tackles in the 49ers' two playoff victories as he's played through the injury this postseason.
Despite the injury, the 12-year veteran said he has no plans to retire after the season.
"I'm not going to retire after this year; I would like to come back and try to get here (the Super Bowl) again," he said. "I realize my career is definitely winding down. I'm not saying I'm going to play another eight years or something like that.
"I want to play at a high level. I don't want to just be a back-up guy, a mentor-guy. I want to help the guys as much as possible, show them all of the stuff I've learned from other guys. It's all just passing the torch, everything you learn from the coaching staffs. I want to do that while I'm playing."