Your GPA gives you a guide as to how you are doing in school and is used to determine which colleges will accept you. At the end of each semester your GPA will be posted so you can see how you’re doing but what if you want to know before it’s posted. You need to know how to work it out for yourself.
There is more than one grading scale but they are all worked out the same way, only the numbers change. To keep it simple, as the 4 point system is the most common, we’ll concentrate on that one.
Firstly each grade has a points total associated to it:
A = 4
B = 3
C = 2
D = 1
In high school the + and – are usually disregarded, while in college they generally add or subtract 0.3 from the whole letter grade so for example a B+ = 3.3 whereas a B- = 2.7.
To calculate your semester un-weighted GPA all you need to do is add the numbers up from each class and divide by the total number of classes. So if you got 3 A’s and a B your GPA = ([3 x 4] + 3)/4 = 3.75
If you want to calculate your weighted GPA you do this in the same way, assigning a points value to each grade, but instead of dividing by the number of classes you divide by the total amount of points the classes were worth. In high school you may be doing honours or AP classes, for these you simply add 0.5 or 1 point to each grade respectively.
So that’s how to calculate this semesters GPA, but how do you add in your previous GPA to get your cumulative GPA? First you need to know how many classes/points your previous GPA is for. You multiply your previous figure by the total classes/points and add this to the total for this semester. You then divide by the sum of classes/points, including the previous ones. As an example James has a GPA of 3.75 from 20 classes. In this semester he has got 2 A’s and 2 B’s. To calculate his cumulative GPA we multiply 3.75 by 20 = 75 add this semesters grades (75 + 4 + 4 + 3 + 3) = 89 and divide by 24 which = 3.71 (rounded). So James’ cumulative GPA is now 3.71.
If your school uses the 9 point scale or any of the others all you need to do is change the amount of points associated with each grade to fit your scale.
Source by David Cutts