my son has a 3.12 gpa for the past 3 years and this year hes getting a 4.8 whats his gpa going to be?

How in the world did he get a 4.8 GPA???

GPA is figured by adding up the numeric values of the grades and dividing by the number grades that were added up. What his GPA will be depends upon how many grades he had during the last 3 years and how many grades he will have this year.

To keep it really simple (and simplistic)...

Assume he had one grade of 3.12 in each of his first three years and one grade of 4.8 this year:

3.12+3.12+3.12+4.8 = 14.16 divided by 4 grades ... 14.16/4 = 3.54 GPA

but, if he had 2 grades of 3.12 in each of the 1st three years and only one grade this year (4.8) then

3.12+3.12+3.12+3.12+3.12+3.12+4.8 = 23.52 divided by 7 grades ... 23.52/7 = 3.36

Thus, just knowing the information you provided here is not enough to answer your question. If we knew how many total classes he took during the 1st three years and how many classes this year, we could calculate a final GPA.

SilverRain's method is a good approximation, IF his assumption of everything being pretty much equal throughout the 4 years is valid.

EDIT:

So...6 classes in each of 3 years: 18 classes with a GPA of 3.12 ... 18*3.12 = 56.16

Assuming he gets straight A's in in all six classes this year:

5*5.0 + 1*4.0 = 29

56.16 + 29 = 85.16 in a total of 24 classes ... 85.16/24 = 3.55 is the best possible GPA he could have.

On the other hand, if he gets 4 A's (5.0 each) and 1 B (4.0) in the AP classes and a B (3.0) in the regular class:

(4*5.0 + 1*4.0) + 1*3.0 = 27.0 for this year gives

56.16 + 27 = 83.16 in 24 classes ... 83.16/24 = 3.46 GPA for 4 years.

Hope this helps.

(3.12 * 3 + 4.8 ) / 4 ( this should be a decent approximation assuming he took about the same amount of hours every semester)

3.54 give or take a few