This GPA calculator will help you figure Grade Point Averages for any number of classes with grades that you want to submit.
You can begin with your current GPA and add additional courses and grades, and calculate how your GPA will change.
Or, again beginning with the current GPA, you can set a target GPA and calculate what average you will need (in a given number of credits) to achieve that target.
Or you can just enter a list of grades without starting from an existing GPA to calculate an average for a semester, or just for major courses, or for any other combination of grades for which you'd like to get an average.