$$ \text{GPA} = \frac{\sum (\text{Grade Point} \times \text{Credit Hours})}{\sum \text{Credit Hours}} $$

Steps:
(01) Convert each course's percentage or letter grade to the corresponding grade point (see UIU Grading System).
(02) Multiply the grade point by the credit hours of the course.
(03) Add up all the results from the previous step.
(04) Divide the total by the sum of all credit hours.

Example:
If you took 3 courses with grades A (1 credit), B+ (3 credits), and B (3 credits):

$$ \begin{aligned} \text{GPA} &= \frac{(4.00 \times 1) + (3.33 \times 3) + (3.00 \times 3)}{1 + 3 + 3} \\ &= \frac{4 + 9.99 + 9}{7} \\ &= 3.29 \end{aligned} $$

$$ \text{CGPA} = \frac{ \text{GPA}_1 \times \text{Credits}_1 + \text{GPA}_2 \times \text{Credits}_2 + \dots }{ \text{Total Credits} } $$

Steps:
(01) Calculate the GPA for each trimester using the formula above.
(02) Multiply each trimester's GPA by the total credit hours of that trimester.
(03) Add up all the results from step 2.
(04) Divide the total by the sum of all credit hours from all trimesters.

Example:
If you completed 2 trimesters with GPA 3.30 (11 credits) and 3.50 (13 credits):

$$ \begin{aligned} \text{CGPA} &= \frac{(3.30 \times 11) + (3.50 \times 13)}{11 + 13} \\ &= \frac{36.3 + 45.5}{24} \\ &= 3.38 \end{aligned} $$