How do colleges calculate GPA

Applying to College
1

Do they just use the GPA on your high school transcript or do they see every grade for your classes and recalculate? For example, if a high school uses a scale like
A=4
B=3
C=2

and someone got a B+ and was given a 3 for their B+, would colleges recalculate that B+ as something like a 3.3 or just give that B+ a 3 as listed on the high school transcript?

2

Also, if on your transcript, your high school weighted your GPA, would colleges recalculate for a non-weighted GPA?

3

Different colleges=different methods.