A GPA is a credit-weighted average of grade points
Not an average of percentages, and not an average of your letter grades either. Each letter maps to a number of grade points — an A is 4.0, a B is 3.0 — and each course's grade points are weighted by how many credits the course carries. A four-credit course counts twice as much as a two-credit one.
That is why a 4.0-scale GPA and a percentage grade are not interconvertible in any general way. An 89% and a 91% might both sit inside your school's A− band or straddle a boundary, depending on a convention your registrar chose. The "percentage to GPA" tables floating around online are institutional conventions written down, not mathematics. We keep ours on a separate reference page and say plainly where they come from.
Weighted, unweighted, and why you get asked for both
An unweighted GPA treats every A as 4.0 regardless of how hard the course was. A weighted GPA adds a bump for honours, AP or IB courses — commonly +0.5 and +1.0 respectively — which is why weighted GPAs can exceed 4.0 and are often reported on a 5.0 scale.
College applications routinely want both: your school's weighted figure, because that is what your transcript shows, and an unweighted figure, because that is the only number comparable across schools with different weighting schemes. Most calculators make you pick a mode and run it twice. This one enters your courses once and returns both, because being asked for both is the normal case.
Worked example
Five courses, mixed credits, two of them advanced:
- English Literature — A− (3.7), 3 credits, regular
- Calculus — B (3.0), 4 credits, AP → weighted 4.0
- Chemistry — B+ (3.3), 4 credits, honours → weighted 3.8
- US History — A (4.0), 3 credits, regular
- Spanish — B− (2.7), 1 credit, regular
Unweighted: (3.7×3 + 3.0×4 + 3.3×4 + 4.0×3 + 2.7×1) ÷ 15 = 51.3 ÷ 15 = 3.42.
Weighted: (3.7×3 + 4.0×4 + 3.8×4 + 4.0×3 + 2.7×1) ÷ 15 = 58.2 ÷ 15 = 3.88.
Notice the credit weighting doing real work. The B− in Spanish is one credit and barely registers — it costs 0.05 of a GPA point. The B in four-credit Calculus costs far more. Dropping a one-credit elective to protect a GPA is almost always the wrong move; the four-credit course is where the leverage is.
The formula
GPA = Σ(pᵢ × cᵢ) ÷ Σcᵢ, where p is the grade points for the course and c is its credits.
We support the 4.0 scale, the 4.3 scale (where an A+ is worth 4.3 rather than being capped at 4.0), and the 5.0 weighted scale used by many US high schools. Which one your school uses is a fact about your school, not about GPA — your registrar or student handbook will say. Getting it wrong shifts every result.
Pass/fail, withdrawal, incomplete and audit credits are excluded from both the numerator and the denominator. They do not raise your GPA and they do not lower it; they simply are not in the average. That is standard at most institutions, and it is why a term of pass/fail courses leaves your GPA exactly where it was.
Where this stops being reliable
Repeated courses are the big one. Some institutions replace the original grade, some average both attempts, and some keep both on the transcript but count only the second — and the difference can be half a grade point. We cannot know which your school does. Transfer credits often carry credit hours without grade points, which changes your credit total but not your GPA. Quarter-system credit hours are not semester credit hours; the usual conversion is 1.5 quarter credits to 1 semester credit. And plus/minus systems versus straight-letter systems produce genuinely different GPAs from identical work.
This calculator applies the standard formula correctly. It cannot apply your registrar's local rules, and where those rules matter, they beat anything on this page.