According to most grading schemes, a score of 64 out of 100 corresponds to a letter grade of D. On the conventional grade-point-average or GPA scale, this grade is also equal to one grade point.
Letter grades are awarded to each numerical grade on a range of 1 to 100 in most American educational systems. The following are the letter grades:
A = 90–100
B is between 80 and 90
70-80 degrees Celsius
D = 60–70
F ranges from 0 to 60.
When issuing a grade, some schools may employ + or – indicators. A 72 out of 100, for example, would be a C-, while a 78 out of 100 would be a C+.