You’ll get an A- on an assignment between 90 and 100 percent of the time. You’re doing well, even with a B. This is an above-average score, between 80% and 89%. There is a 59–69% chance that this grade is good enough to pass. What does a grade of 88-100 on a letter scale mean? The formula for letter grades. Use the following conversion formula to find out what letter grade you got on a midterm: If your score is 88-100, you get an A, 78-87, a B, 68-77, a C, 58-67, a D, and 57 or less, an F.A…