Arrange your transcripts into three piles, one pile for each of the three grading systems.
Convert all transcripts using number-grading systems to letter-grading systems. Use a new piece of paper to be your pseudo-transcript for the number-grading system pile. Carry the credit-hours for each course on your original transcript onto the pseudo-transcript. Use the following scale to rewrite your transcripts:
A+: 97 to 100 percent
A: 94 to 96 percent
A-: 90 to 93 percent
B+: 87 to 89 percent
B: 84 to 86 percent
B-: 80 to 83 percent
C+: 77 to 79 percent
C: 74 to 76 percent
C-: 70 to 73 percent
D+: 67 to 69 percent
D: 64 to 66 percent
D-: 60 to 63 percent
F: 0 to 59 percent
Place the pseudo-transcripts into the letter-grade pile.
Convert the letter-grade transcripts into GPA transcripts. Use a new piece of paper to be your pseudo-transcript. Convert the letter grade into a GPA grade for each course in your pile of letter-grade transcripts. Carry over the credit hours for each class. Use the following scale for conversion:
A or above: 4.0
A-: 3.7
B+: 3.3
B: 3.0
B-: 2.7
C+: 2.3
C: 2.0
C-: 1.7
D+: 1.3
D: 1.0
D-: 0.7
F: 0.0
Place the GPA-pseudo transcript into the GPA transcript pile.
Calculate your overall GPA. Multiply the GPA for each course by its credit hours. For example, if you received a 2.9 in your calculus course worth five credit hours, write 2.9*5 = 14.5. Add these values for every course, and divide by the total number of credit hours. This final value is your overall GPA, accounting for all your transcripts.