The scale, and the first thing it does not tell you
On the standard US 4.0 scale, College Board lists it like this: A is 4.0, B is 3.0, C is 2.0, D is 1.0, and E or F is 0.0. Their percentage bands run A for 90 to 100, B for 80 to 89, C for 70 to 79, D for 66 to 69, and failing below 65.
Then comes the sentence people skip. College Board says plainly that this is not necessarily a formula for calculating your true GPA, because some schools do not use pluses and minuses and others have different grade cutoffs.
So an A- might be 3.7 at one school and 4.0 at another. A B+ might be 3.3 or 3.0. A 89 might round up or might not. Before computing anything, find your own school's table, usually in the student handbook. That table overrides everything in this article.
It is a weighted average, and the weight is credits
The mistake almost everyone makes on their first attempt: add up the grade points and divide by the number of classes.
Dividing by class count is only right if every class carries the same credit. Most do not. A full-year course is often worth more than a semester course, a lab science more than an elective, and the GPA is built to reflect that.
The real formula: multiply each class's grade points by its credits, add those products up, then divide by the total credits. Credits act as weights.
A worked term. Four classes: English, 4.0, 1 credit. Chemistry, 3.0, 1 credit. Art, 4.0, 0.5 credit. History, 2.0, 1 credit.
The naive average is 13 divided by 4, which is 3.25. The credit-weighted one: 4.0 plus 3.0 plus 2.0 plus 2.0, which is 11.0 grade points across 3.5 credits, giving 3.14. Same grades, a tenth lower, because the A in Art only counted for half. Small here, and it compounds across a transcript. The GPA calculator takes credits per class for exactly this reason, and it defaults to 1 so you can ignore them if your school does.
Cumulative GPA works the same way across every term you have taken: total grade points earned divided by total credits attempted. Not an average of term GPAs, which would let a light term count the same as a heavy one.
Weighted GPA, and why yours might be above 4.0
College Board notes that some schools use a weighted system in which AP and honors courses are assigned higher GPA points. Nothing more specific appears on the numbers, and the vagueness is honest: there is no national standard.
The common convention is an extra point for AP and IB, so an A in an AP class scores 5.0, and half a point for honors, so an A scores 4.5. Plenty of schools do something else. Some weight honors and AP equally, some do not weight honors at all, some cap the whole thing.
The effect is a GPA that can run above 4.0, which confuses anyone comparing across schools and is the reason admissions offices recalculate. Many colleges strip the weighting and rebuild an unweighted GPA from your transcript using their own table, so the number on your report card and the number they look at can differ.
Two things follow. Know both your weighted and unweighted figures, because different forms ask for different ones. And do not chase the weighted number by loading up on courses you will do badly in: a B in AP is 4.0 weighted, and so is an A in the regular section, and one of those is a great deal more work.
Rounding, repeats and the things that quietly move it
Rounding happens at the letter grade, not at the GPA, and schools differ on it. An 89.5 is an A at some schools and a B at others. Once it becomes a B, it is 3.0 and the half point that would have made it an A is gone. The percentage calculator will tell you exactly where a final exam needs to land to cross a boundary, which is worth knowing in the last week of a term.
Retaken courses vary even more. Some schools replace the old grade, some average the two, some keep both on the transcript and the GPA. Ask before assuming a retake will erase anything.
Pass/fail courses usually carry credit but no grade points, and most schools exclude them from the GPA entirely rather than counting them as zero. Check, because the alternative is a course dragging the average down while appearing harmless.
Transfer credit is the last one. A GPA from another institution normally does not merge into the new one. The credits transfer, the grade points often do not, and the new GPA starts fresh.
Working out what you need
The useful calculation is not your current GPA but what the next term has to produce to hit a target.
Say you have 60 credits at a 2.9 and want a 3.0 by the end of a 15-credit term. You have 174 grade points. A 3.0 across 75 credits needs 225. So the term has to produce 51 points across 15 credits, which is a 3.4 average. Achievable. A 3.2 target would need 66 points, a 4.4 average, which is not.
Doing that sum once, early, tells you whether the target is real. The GPA calculator has a mode for it, and it is the one worth opening in the first week rather than the last.
None of this is guidance on what GPA you need for any particular program. That number belongs to the program, and the only reliable place to get it is from them.
Questions people ask
Multiply each class's grade points by its credits, add those together, then divide by total credits. On the standard scale A is 4.0, B 3.0, C 2.0, D 1.0 and F 0. Dividing by the number of classes instead of total credits is the usual mistake and gives the wrong answer whenever classes carry different credit.
Unweighted caps at 4.0 and scores every class on the same scale. Weighted gives extra points to harder courses, commonly an added 1.0 for AP and IB and 0.5 for honors, so it can exceed 4.0. College Board notes the practice but no fixed numbers, because schools set their own, and many colleges recalculate an unweighted figure anyway.
On a weighted scale, yes. An A in an AP class commonly scores 5.0, so a student with several AP courses can carry a weighted GPA above 4.0. On an unweighted scale 4.0 is the ceiling. Forms and applications usually specify which one they want.
Work in grade points, not averages. Multiply your current GPA by your credits to get points earned, multiply the target GPA by the credits you will have afterwards to get points needed, and the difference divided by the coming term's credits is the average you must hit. Sixty credits at 2.9 reaching 3.0 over a 15-credit term needs a 3.4 that term.
Usually not. They typically carry credit toward graduation but no grade points, and most schools exclude them from the GPA calculation rather than treating a pass as zero. Confirm with your registrar, because a school that does count them can pull the average down unexpectedly.
It depends entirely on the school. Some replace the original grade, some average both attempts, and some keep both on the transcript and in the GPA. Ask before retaking on the assumption that the first grade will disappear.