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.

Standardised vs custom grading scales

US schools commonly use the 90/80/70/60 scale shown above. Other systems:

The grading scale itself doesn&apos;t change what a student knows — only the threshold for documenting it. When setting a custom scale, communicate it upfront so students calibrate their preparation.

Weighting categories beyond quizzes

A typical course gradebook weights multiple components:

The weighted total is: (quiz_avg × 0.20) + (hw_avg × 0.15) + ... = course grade. Most LMSs handle this automatically once you tag each assessment with its category. SimpleQuizMaker exports per-quiz scores as CSV; your LMS (Canvas, Schoology, Blackboard) handles the weighting.

Common grading pitfalls

Grading transparency

Best practice: publish the grading scheme on day one with weights, drop policies, and curve rules. Stick to what&apos;s published. End-of-semester surprises ("oh, I&apos;m adding a curve / changing weights") undermine trust even when they help students.

Related reading

Calculating equal-weight quizzes

The simplest case: every question is worth the same.

If you grade by hand, a quick mental math approach: count missed items, divide by total to get error rate, subtract from 100. 2 missed out of 20 = 10% error = 90%.

Weighted scoring

When some questions are worth more than others (typical for unit tests with a mix of MCQ and short-answer):

Worked example: 5 MCQs worth 2 points each (10 total) + 2 short answers worth 5 points each (10 total) = 20 possible points. Student gets 4 MCQs right (8 points) and full credit on one short answer + half credit on the other (5 + 2.5 = 7.5 points). Total earned = 15.5 / 20 = 77.5%.

Partial credit and rubric-based scoring

For non-binary items:

Most LMS gradebooks support all three. Choose based on item type.

Bonus questions

Two conventions:

Pick one and announce it before the quiz. Mixed conventions confuse students and parents.

Curving and dropping

Communicate curve policy upfront; surprise curving creates trust issues.

Letter grade mapping

US conventions vary by district but common cuts:

European conventions vary widely; UK uses percentage bands tied to degree classifications (1st, 2:1, 2:2, 3rd, Fail).

Common scoring mistakes

Use SimpleQuizMaker for auto-scoring →