Course work is measured in “units” or “credit hours.” Generally, a class that meets for three hours of lectures or discussion a week carries three units of credit – one hour of undergraduate credit means one hour of lecture and two hours of homework, whereas one hour of graduate credit means one hour of lecture and five hours of homework. An average class-load at the bachelor’s degree level is about 15 units per semester, which means about 45 hours of attendance and study are expected each week. At the graduate level the average class-load is about nine units per semester, so about 54 hours of attendance and study are expected each week.
When referring to “units” or “credit hours” people are generally talking about units in a semester system. Each unit in a quarter system equals 2/3 of a semester-unit. So a student who completes 30 semester-units each year in a semester system is doing the same amount of work as a student who completes 45 quarter-units.