The Carnegie Unit and the Student Hour are strictly time-based references for measuring educational attainment used by American universities and colleges; the Carnegie Unit assesses secondary school attainment, and the Student Hour, derived from the Carnegie Unit, assesses collegiate attainment.
As per its original definition, the Carnegie Unit is 120 hours of class or contact time with an instructor over the course of a year at the secondary (American high school) level. Strictly speaking, this breaks down into a single one-hour meeting, on each of five days per week for a total of 24 weeks per year. However, knowing that classes usually meet for 50 minutes yields a value of 30 weeks per year. However, further complicating the computation is the fact that American schools typically meet 180 days, or 36 academic weeks, a year. A semester (one-half of a full year) earns 1/2 a Carnegie Unit.[1]
The Student Hour is approximately 12 hours of class or contact time, approximately 1/10 of the Carnegie Unit (as explained below). As it is used today, a Student Hour is the equivalent of one hour (50 minutes) of lecture time for a single student per week over the course of a semester, usually 14 to 16 weeks.