GPA, Percentages and Letter Grades Explained

Three different things

• Percentage: your score in a course, such as 87%.
• Letter grade: a band that percentage falls into, such as B+.
• GPA (grade point average): the average of grade points across courses, where each letter grade is worth a number of points.

An example of a US-style scale

One commonly used US scale gives 93% and above an A (4.0), 90 to 92% an A- (3.7), 87 to 89% a B+ (3.3), 83 to 86% a B (3.0), 80 to 82% a B- (2.7), and so on down to an F (0.0) below 60%. Many schools use this or something close to it, but cut-offs vary, and some schools do not use plus and minus grades at all.

Calculating a credit-weighted GPA

Courses with more credits count for more. Multiply each course's grade points by its credit hours, add the results, and divide by the total credit hours.

Example: A 4-credit course with an A (4.0), and a 2-credit course with a B- (2.7): (4.0 × 4 + 2.7 × 2) ÷ (4 + 2) = 21.4 ÷ 6 = 3.57. A simple average of 4.0 and 2.7 would give 3.35, which is wrong because it ignores the credits.

Other systems

Countries and institutions use very different systems. In the UK, degree classifications are commonly based on average percentages, with first-class honours typically starting around 70%, but the exact rules belong to each university. Some countries grade out of 10 or 20, and others use letters on different scales. A percentage that is excellent in one system may be average in another, so conversions between systems are rough at best.

Cumulative and semester GPA

A semester GPA covers one term. A cumulative GPA combines all terms, again weighted by credits. Repeated courses, pass/fail courses, transfer credits and withdrawals are treated differently by different registrars, so check how your institution handles them before predicting your cumulative GPA.

Common conversion mistakes

• Averaging percentages across courses without weighting by credits.
• Applying another institution's letter-grade cut-offs to your own marks.
• Rounding each course before averaging, which can shift the result slightly. Keep full precision until the end.
• Counting pass/fail or audit courses that your institution leaves out of the GPA.
• Forgetting that a repeated course may replace the earlier grade or may be averaged with it, depending on policy.

Practical advice

• Use the scale printed by your own institution, not a generic one.
• Keep percentages and GPA separate in your head: you can think about a course in percentages and a term in GPA.
• When planning, work backward: decide the GPA you want, find the grade each course needs, then use a final-exam calculator to see the score required on each final.