How a credit-weighted GPA is calculated
Grade point average is a weighted mean, not a simple average of grades. Each course contributes its grade points multiplied by its credit hours, those products are summed, and the total is divided by total credits. In formula terms: GPA equals the sum of (grade points times credits) divided by the sum of credits.
Weighting by credits is what makes a four-credit course count more than a one-credit course. A student who does poorly in a lab worth one credit and well in a four-credit core course ends up with a GPA close to the core course grade, which is the intended behaviour. Averaging the letter grades without weights would give a materially different and less meaningful number.
The calculator sums grade points and credits across every row you add, shows both totals, and divides. Rows with zero credits contribute nothing to either total and therefore do not move the GPA.
The grade scale used here
The scale is the common US 4.0 scale with pluses and minuses: A+ is 4.3, A is 4.0, A- is 3.7, B+ is 3.3, B is 3.0, B- is 2.7, C+ is 2.3, C is 2.0, C- is 1.7, D is 1.0, and F is 0.
Institutions vary, and the A+ value is the most variable point. Many schools cap A+ at 4.0, so that a perfect transcript yields exactly 4.00 and no higher. Some do not offer A+ at all. Some include D+ and D- grades, which this scale does not. If your institution caps A+ at 4.0, select A instead of A+ to reproduce its arithmetic.
Credits also go by different names: credit hours, units, semester hours, or course weights. Whatever the label, enter the number your institution uses to weight the course, since the ratio between courses is what matters rather than the absolute scale.
A worked example
Three courses: an A in a 3-credit course, a B+ in a 3-credit course, and an A- in a 4-credit course. Convert each grade to points and multiply by credits. A is 4.0 times 3, which is 12.0. B+ is 3.3 times 3, which is 9.9. A- is 3.7 times 4, which is 14.8.
Total grade points are 12.0 plus 9.9 plus 14.8, or 36.7. Total credits are 3 plus 3 plus 4, or 10. GPA is 36.7 divided by 10, which is 3.67.
Compare that against the unweighted average of the three grade points, which is (4.0 plus 3.3 plus 3.7) divided by 3, or 3.67 as well in this particular case because the credits happen to be nearly balanced. Change the A- course to 1 credit and the weighted GPA becomes (12.0 plus 9.9 plus 3.7) divided by 7, or 3.66, while the unweighted average stays at 3.67. The divergence grows as credit loads become more uneven.
Term GPA, cumulative GPA, and target grades
Entering only the current semester's courses gives a term GPA. To get a cumulative GPA, add a row representing everything completed so far: put your total accumulated credits in the credits field and choose a grade whose points match your existing GPA. That only works exactly when your current GPA coincides with one of the listed grade values, so for arbitrary values the cleaner method is to compute it by hand: multiply prior GPA by prior credits to get prior grade points, add the new term's grade points, and divide by the combined credits.
For example, a student with 60 credits at a 3.40 GPA has 204 prior grade points. Adding the 10-credit term above with 36.7 points gives 240.7 points across 70 credits, a cumulative GPA of 3.44. A single strong term moves a large cumulative record only slightly, which is the practical consequence of credit weighting.
The same arithmetic answers the target question in reverse. If you need a 3.50 cumulative across 70 credits, you need 245 total grade points, so with 204 already banked you need 41 points from 10 credits, an average of 4.1 per credit. That is above an A, which tells you the target is not reachable this term under a scale where A is 4.0.
What the calculation does not handle
Pass or fail courses are excluded from GPA at most institutions: they award credit without grade points, and including them as a grade here would distort the result. Withdrawals, incompletes, and audited courses similarly carry no grade points in most schemes. Leave all of these out rather than assigning them a value.
Repeated courses follow institution-specific rules. Some replace the original grade entirely, some average the attempts, and some count both. The tool has no repeat handling, so enter whichever rows your institution's policy would actually count.
Weighted high school GPAs, where honors and AP courses are graded on a 5.0 scale, are not supported by this 4.0 scale. Neither are transfer credits, which many institutions accept for credit without importing the grade points, and which therefore change your credit total without changing your GPA. Your official transcript remains the authority on all of these.