How to Calculate Quiz Grades (Including Weighted Averages)
TL;DR. Quiz grades are easier than they look. This covers percentage, letter grade conversion, weighted averages, dropping the lowest score, extra credit, and curve-fitting.
Percentage from raw score
Points earned ÷ Points possible × 100.
Example: 17/20 = 85%.
Letter grade (US standard)
| % | Letter |
|---|---|
| 90–100 | A |
| 80–89 | B |
| 70–79 | C |
| 60–69 | D |
| <60 | F |
Many schools use +/-: A− 90–92, A 93–100, etc.
Weighted average across multiple quizzes
(Q1×W1 + Q2×W2 + … + Qn×Wn) ÷ (W1 + W2 + … + Wn)
Example: 80% (W1), 85% (W1), 90% (W2), 75% (W1):
= (80 + 85 + 180 + 75) / 5 = 84%.
Dropping the lowest score
Example: 60, 70, 80, 90, 100. Mean = 80. Without 60: 85. Final = 85%.
Curve-fitting
If a quiz was harder than intended, curve scores.
Simplest curve: add a constant. Highest = 78 → add 22 to everyone, top becomes 100.
Extra credit
Two approaches:
Most teachers use the first, capping at 100%.
Excel formula
Percentage: ROUND(POINTS_EARNED / POINTS_POSSIBLE * 100, 2)
Letter: IF(P>=90,"A",IF(P>=80,"B",IF(P>=70,"C",IF(P>=60,"D","F"))))
Auto-scoring in SimpleQuizMaker
SimpleQuizMaker computes percentage and letter grade automatically. Set your scale, configure weighting and drop-lowest at the gradebook level.
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Sarah Mitchell
Curriculum Designer & Former High School Teacher
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