A credit hour is the unit colleges use to measure how much a course counts, based on the time a student is expected to spend in class and on outside work each week.

The official definition

US federal regulations define a credit hour as an amount of student work that reasonably approximates at least one hour of classroom instruction plus a minimum of two hours of out-of-class work each week for about fifteen weeks (one semester hour), or ten to twelve weeks (one quarter hour). The full wording is in 34 CFR 600.2. Colleges apply it to labs, internships and studio courses with equivalent workloads.

In practice, a typical lecture course is 3 credits: three hours in class and about six hours of reading, problem sets and studying each week.

Why credits change your GPA

Your GPA weights each grade by its credits. Compare two students with an A and a C:

  • Student 1: A in a 4-credit lab science (16 quality points), C in a 1-credit seminar (2 points). 18 ÷ 5 = 3.60
  • Student 2: A in the 1-credit seminar (4 points), C in the 4-credit science (8 points). 12 ÷ 5 = 2.40

Same letters, very different results. That is why the GPA calculator and the cumulative GPA calculator ask for credits next to every grade.

High school credits

High schools usually count “credits” per course (often one credit for a year-long class, half for a semester), and graduation requirements are written in those units. The idea is the same: more time, more weight. If your school weights classes differently, see weighted GPA, and for how a single semester grade is built, try the semester grade calculator.

Related: grade point average · cumulative GPA

Frequently asked questions

How many hours a week is a 3-credit class?
Under the federal definition, each semester credit hour reflects about one hour of class plus at least two hours of outside work per week for roughly 15 weeks. So a 3-credit class means about 3 hours in class and 6 hours of homework and study each week.
What is the difference between a credit hour and a contact hour?
A contact hour is time actually spent in class with an instructor. A credit hour is the unit counted toward your degree and GPA, and it assumes outside work on top of class time. A lab can have more contact hours than credit hours because so much of the work happens in the room.