College credit hours are calculated based on the time students spend in class and studying. One credit hour usually represents three total hours of work per week over a 15-week semester, with one of those three hours consisting of direct classroom instruction and the remaining hours consisting of individual study.
To illustrate the concept of credit hours, consider the example of Cornell University. At Cornell, full-time students typically complete 15 course credits per semester, representing approximately 15 hours of classroom time and 30 hours of individual study time per week.
Some college courses do not lend themselves to the traditional mix of one weekly hour of class time and two weekly hours of study time per credit hour. Laboratory courses, internships and other relevant academic activities may also play into the number of credit hours assigned to certain courses like physical science labs and research seminars.