Contact your university registrar to determine the scale that your school uses to convert numerical grades to letter grades. For example, the University of Washington awards an A for a 3.9 to 4.0, an A- for a 3.5 to 3.8, a B+ for 3.2 to 3.4 and so on.
Consult your transcript to check your cumulative grade point average. If you do not have your transcript, you may be able to check your GPA online through your university's registrar's office or you may be able to order a copy of your transcript.
Convert your grade point average to a letter grade using the scale set by your school. Using the University of Washington's grading scale, if your grade point average equaled 3.6, that would convert to an A- letter grade.