Grade Point Average is calculated by multiplying each course's grade points by its credit hours, summing those products, then dividing by total credit hours. This makes GPA a credit-weighted average, not a simple average of grades. A 4-credit course counts four times as heavily as a 1-credit course.
On the standard 4.0 scale, letter grades convert to grade points: A = 4.0, B = 3.0, C = 2.0, D = 1.0, F = 0. A student earning a B in a 3-credit course and an A in a 3-credit course has GPA = (3.0 × 3 + 4.0 × 3) / (3 + 3) = 21 / 6 = 3.50. If plus/minus grades are used, an A− = 3.7, B+ = 3.3, B− = 2.7, and so on, with A+ sometimes equal to 4.0 or 4.3 depending on the institution.
Weighted GPA and honors/AP courses
A weighted GPA adds bonus grade points for more rigorous courses. Honors courses commonly add 0.5 points (so an A in an Honors class = 4.5) and AP/IB courses add 1.0 point (A = 5.0). A student with all As in AP courses would have a weighted GPA of 5.0 on a 5.0 scale, while the same grades on unweighted scale would be 4.0.
This makes weighted and unweighted GPAs incomparable across schools that use different scales. Colleges typically recalculate applicants' GPAs using their own criteria, because a 3.9 weighted GPA at one high school might reflect a harder or easier course load than a 3.9 at another. Some colleges specifically request unweighted GPA to enable more consistent comparison.
Cumulative vs term GPA and the effect of retaken courses
Cumulative GPA includes all courses from the start of study, while term (or semester) GPA covers only the current period. Because cumulative GPA is credit-weighted across all terms, it changes slowly — a single strong or weak semester has diminishing impact as more credits accumulate. Early low grades are hard to overcome: a student with a 2.5 GPA after 60 credits needs to earn a 3.5 average for the next 60 credits just to reach a 3.0 cumulative GPA.
Policies on repeated courses vary. Some schools replace the original grade with the new one in the GPA calculation; others average both; others exclude the first attempt from the GPA but keep it on the transcript. Students retaking courses to improve their GPA should check their institution's specific policy before assuming the strategy will work as expected.