I didn't know this, so I looked it up.
Regular season/postseason rules
- Limit of 14 padded practices during the regular season, 11 of which must be held during the first 11 weeks (club may hold two padded practices during only one week) with remaining three during the final six weeks.
- One padded practice per week in postseason.
- Padded practices limited to three hours plus a walk-through with position coaches not to exceed 30 minutes.
- Bye weeks – four consecutive days off.
Source: NFLPA summary of main terms of the 2011 collective bargaining agreement.