Looks nice!
I actually made a java app that can calculate gpa and convert to 4.0 scale (I guess I'm just not a fan of excel) and was thinking of making it into an android app but never got around to it.
You should think about adding a section for past courses so that a person can add all of their previous courses and final grades to see what their cumulative average is (and to convert to 4.0 cgpa). And also be able to section them off so that sessional average can be calculated too.
Also, for the current courses where it has all the assignments and marks, I think it would be useful to make an option to add more assessments since some courses have a lot of labs and assignments and stuff.
Just some ideas