A grade point average turns a term of separate grades into one number by weighting each grade by the size of the course it came from. At Duke University, as at other schools, a registrar multiplies every grade’s point value by that course’s credit hours, adds those totals together, then divides the sum by the total credits attempted. A five-credit course pulls the average harder than a one-credit one, because the weight is the credit load, not the grade alone.
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Duke University’s registrar spells out the arithmetic plainly: multiply each course’s credit hours by the grade point value earned, add every course’s total, then divide by the sum of the credits. Portland State’s registrar walks through a worked example. A student earns a B- in one three-credit course and a C in another. The same term brings an A in a two-credit course, a C- in a three-credit course and a D+ in a four-credit course. Those grades add up to 32.34 quality points across 15 credit hours, for a term GPA of 2.15.
What number does each letter grade carry?
The most common scale runs from A at 4.0 down to F at 0.0, in whole-point steps for B, C and D. Stanford uses a finer 4.3 scale, where an A- carries 3.7 points and a C+ carries 2.3, so a grade’s exact decimal value depends on the institution’s own table rather than a fixed national standard. The University of Hertfordshire converts each module mark, out of 100, into a Grade Point on a 0 to 4.5 scale before averaging it with every other module a student has taken.
Oxford Brookes runs the same idea with its own numbers. Each final grade converts to one of nine scores, topping out at 4.5 for an A+, and that score is multiplied by the module’s credits to produce the grade points that feed the average. The university caps the reported GPA at 4.00 even though the top grade point is 4.5, a deliberate compromise it says keeps its figure comparable with the more common 4.00 international ceiling while still reflecting how UK marking runs a wider scale at the very top.
Which grades never enter the sum?
A grade with no numerical value drops out of both sides of the division, not just the top. Nebraska excludes “P”, “N”, “I”, “W” and “NR” symbols from its GPA calculation entirely, so a student’s Pass/No Pass course affects neither the quality points nor the credit total used to compute the average. Portland State applies the same principle to Pass/No Pass, credit-by-exam, correspondence and audited courses, and it never counts transfer credit from another college in the calculation at all. The federal government’s own transcript study, which standardises grades across US high schools for comparison, likewise drops pass/fail and audited courses before dividing total grade points by total credits attempted.
A failed course is treated differently from an ungraded one. Duke uses all regularly graded courses in the GPA, but a course taken as Credit/No Credit, Pass/Fail or Satisfactory/Unsatisfactory contributes no grade at all, not even a failing one. Oxford Brookes’ GPA likewise includes modules a student has failed.
Why does credit weighting change the outcome?
The Conversation sets out why the credit value matters as much as the letter grade. Take a student who earns A, B and B in three five-credit courses and an A in one ten-credit course. Multiplying each grade’s numerical equivalent by its credit value and summing the results gives 90 grade points. Dividing that by the 25 total credits gives a GPA of 3.6. Swap the credit values for 20, 20, 20 and 40, keeping every grade the same, and the GPA still comes out at 3.6, because only the ratio between the weights matters, not their absolute size.
Stanford’s own example runs the same logic with unit values instead of credit hours: an A in a five-unit course contributes 20 grade points, while a C+ in a three-unit course contributes 6.9, and the GPA is the sum of every course’s points divided by the sum of every course’s units.
How precise is the final figure?
Institutions differ on how far they carry the decimal, and none of them round up. Nebraska truncates its reported GPA to the thousandth decimal place. Portland State truncates to two decimal points. Duke truncates to three. A semester GPA and a cumulative GPA are calculated the same way but over different windows: Duke recalculates the cumulative figure from every course a student has taken rather than averaging each semester’s GPA together.
Does the number mean the same thing everywhere?
Not quite. Times Higher Education notes that GPA is mainly a US convention, used across American high schools and colleges on a 0 to 4 scale, with some students able to reach 5.0 through weighted advanced coursework. Oxford Brookes describes itself as the first UK higher education institution to award a GPA alongside the traditional Honours classification, aimed at making a UK degree easier for international employers and postgraduate admissions offices to read. Hertfordshire’s GPA, capped at 4.5 rather than 4.0, applies only to undergraduates who started their course in September 2017 or later, and it sits beside a degree classification rather than replacing it.
The comparison problem is not new. The Conversation points out that a GPA is only as trustworthy as the grades feeding it, and pooling grades from different courses and instructors does nothing to make those grades more comparable in the first place. Grading scales also differ considerably across institutions and countries, and conversion tables exist for comparing them.
