For SJSU and other CSUs other than CPSLO, calculate HS GPA the same as UC weighted capped HS GPA, except that each semester of college course counts as two (honors) courses and grades instead of one.
For engineering majors at SJSU, you also need to calculate a math GPA (it is not obvious whether honors points are added for the math GPA).
For SJSU, multiply the HS GPA by 800, then add any applicable points for local area, etc. (see Impaction | Admissions ). For engineering majors, add 400 times math GPA. Then compare to the threshold numbers found at Freshmen Impaction Results | Admissions , but be aware that the thresholds for this and future years can change somewhat compared to the most recent completed admission cycle.
Other CSUs will have their own formulae for calculating their admission index, and they will set their own thresholds for each major.