GPA can be calculated by adding up your grades as points. For example for my school, an A is 4, B is 3, and so on and so forth. Depending on how many subjects you have as grades, you add all those up, then divide it by how many subjects you have. Say I have all A’s in 7 subjects, I multiply 4 by 7 and get 28. I then divide by 7 because that is how many periods/subjects I have. I get a 4.0 GPA, which is how to calculate it. I don’t know the other question, but I hope this helps.