Hi, I'm a finance person by training, here's how I calculate my science gpa:
1) total number of semester hours of (science & math) courses with As earned divided by
2) total semester hours (science & math) As + Bs earned. That will give you a percent i.e. .45, add 3.0 to that, and that's your science GPA.
This presumes no C's earned. If any C's earned, i.e. 3 hours C earned, subtract three hours of "A" in the denominator (step 1) and include total hours A, B, C in the denominator.
PS I have a graduate degree. This is not included in science/nonscience GPA on the Amcas form, it is included SEPARATELY. It may be a talking point, but school's I've spoken with look at undergraduate GPA when deciding which candidates to interview; likely because it's too tough to compare my graduate grades in management with another student's sociology master's degree with a PhD in biophysics. Conversely, undergraduate courses completed now CAN increase your undergraduate GPA.