How many fists of slack should a seat belt across the chest have?

A properly adjusted seat belt across the chest should have enough slack to allow for comfort but should be snug enough to restrain the occupant in the event of a crash. A common guideline suggests that there should be about one to two fingers' width of space between the belt and the body, rather than measuring in fists of slack. This ensures that the seat belt is effective without being overly tight or restrictive. Always refer to the vehicle's owner manual for specific recommendations.