Question: what will a c do to my gpa?
Answer: Yes, it will inevitability make the GPA go down. ... For example, if you had only 1 course (3 credit) and your GPA is 4.0, having another course of C would make your GPA 3.0. Having 100 courses (each of 3 credit) with a GPA of 4.0, then having a C for another course would make it 3.98. So, yes, it will go down.