For property-carrying drivers the main limits are 11 hours of driving within a 14-hour on-duty window after 10 consecutive hours off, a 30 minute break after 8 hours of driving, and 60 hours on duty in 7 days or 70 hours in 8 days.
The rules have exceptions, such as short-haul and adverse driving condition provisions. Oversize permits add their own limits on when a load may move, so legal hours of service do not mean legal permit hours.
Regulation: 49 CFR 395.3.