How to Calculate GPA from Credits and Grades
Two students can finish a term with the same average mark and different grade point averages, because GPA gives more weight to modules with more credits. A good grade in a substantial module counts for more than the same grade in a short one.
The arithmetic is simple once the weights are clear, but hand calculations go wrong when credits are forgotten or scales are mixed. GPA Calculator takes credits and grades and returns the weighted average.
Quick answer
Multiply each grade’s point value by the module’s credits, add the results, then divide by the total credits. On a four-point scale, a 20-credit module at 3.7 and a 10-credit module at 3.0 give (74 + 30) ÷ 30 = 3.47. Use the grade points your own institution publishes rather than converting marks yourself.
The formula, with a worked example
GPA = sum of (grade points × credits) ÷ sum of credits.
Suppose three modules: 20 credits at 3.7, 10 credits at 3.0 and 10 credits at 4.0. The products are 74, 30 and 40. The total is 144 over 40 credits, so the GPA is 3.6.
Notice what happened: the strongest grade was in the smallest module, so it lifted the result less than the 20-credit module did. That weighting is the whole point. A simple average of 3.7, 3.0 and 4.0 would give 3.57, which is close here but can diverge sharply when credit sizes vary.
Where the grade points come from
Most institutions publish a conversion table: percentage bands mapped to letter grades, and letters mapped to points. Some use a 4.0 scale, some 4.3, and some report classifications rather than a GPA at all. Do not borrow another university’s table; a mark of 70% might be a first-class result in one system and a B in another.
If your transcript shows percentages and you need to convert them, use the published table for your programme. The Percentage Calculator can handle the arithmetic of a weighted average, but the mapping from marks to points still has to come from your handbook. When comparing programmes, look at how each one calculates its average before reading anything into the numbers; our guide to choosing a programme covers the questions worth asking.
What to include, and what to leave out
Rules differ on resits, pass/fail modules, placements and transfer credits. A failed module that is excluded from the calculation can change the result more than a good grade elsewhere. Check three things before you trust a number:
- Whether every module counts, or only the best ones.
- Whether credits from another institution are included and at what value.
- Whether the result is rounded at the end or at each step.
Round only at the final step. Keeping full precision until then avoids small errors that push a borderline result into the wrong band.
Enter your credits and grade points in GPA Calculator to get a weighted result and see how much each module contributes. Then compare it with your institution’s own worked example; if the two disagree, the handbook is the authority.
Common questions
How do I work out a credit-weighted GPA?
Multiply each grade's point value by the module's credits, add those products, then divide by the total credits. For example, 20 credits at 3.7 and 10 credits at 3.0 give (74 + 30) ÷ 30 = 3.47. Use the grade points your own institution publishes instead of converting marks yourself.
Why is my GPA different from a simple average of my grades?
GPA gives more weight to modules with more credits, so a strong grade in a short module lifts the result less than the same grade in a substantial one. A simple average treats every module equally. When credit sizes vary, the two numbers can diverge sharply, which is why weighting matters.
Which grade point scale should I use?
Use the conversion table published by your own institution. Most institutions map percentage bands to letter grades and letters to points, and some use a 4.0 scale while others use 4.3 or report classifications instead of a GPA. Do not borrow another university's table, because the same mark can map differently.