Grade Curve Calculator

Estimate how different grading curves would affect your class grade. Enter raw scores, pick a curve method, and see the before/after. This is a student estimation tool only—real curves are set by your instructor.

Enter class scores

Minimum 3 scores needed. Name and ID optional. Scores are 0–100.

Name / ID (optional) Score

Select curve method

All scores will be increased by this amount (max 100).
Class Average (Before)
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Class Average (After)
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Average Gain
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Class results
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Score breakdown

Name / ID Raw Score Curved Score Grade

Everything stays in your browser — nothing is uploaded. Disclaimer: This tool estimates how curves would work mathematically. Your instructor will set the actual curve, if any. This is for educational exploration only.

How each curve method works

1. Flat (Additive) Curve

Add a fixed number of points to every student's score, then cap results at 100. Useful when an exam was unexpectedly hard.

curved_score = min(raw_score + points, 100) where: raw_score = original score (0–100) points = fixed points added (user-specified) Worked example (add 7 points): Raw scores: 78, 85, 92 Curved scores: min(78+7, 100)=85, min(85+7, 100)=92, min(92+7, 100)=99

2. Scaled-to-Top Curve

Make the highest score equal 100 and scale all others proportionally. If the best student got 92%, everyone else moves up proportionally.

curved_score = (raw_score / max_score) × 100 where: raw_score = original score (0–100) max_score = highest score in the class Worked example (max score is 92): Raw scores: 78, 85, 92 Curved scores: (78/92)×100=84.8, (85/92)×100=92.4, (92/92)×100=100

3. Square-Root Curve

A gentler curve that compresses the scale. High-performing students get less of a boost than with scaling, and struggling students get more help.

curved_score = round(√(raw_score × 100)) where: raw_score = original score as a decimal (0–100) Worked example: Raw scores: 49, 64, 81 Curved scores: round(√(49×100))=70, round(√(64×100))=80, round(√(81×100))=90

4. Percentile (Rank-Based) Curve

Rank students from highest to lowest score, then assign letter grades by percentile bands instead of fixed score cutoffs. The top 10% get A, next 25% get B, and so on.

grade = letter_band(percentile_rank) where: percentile_rank = (students_ranked_below + 0.5) / total_students × 100 letter_band = A if in top 10%, B if next 25%, C if next 30%, D if next 20%, F otherwise Worked example (10 students, using default bands A=10%, B=25%, C=30%, D=20%, F=15%): Sorted raw scores: 92, 88, 85, 82, 79, 76, 73, 70, 65, 60 Percentile ranks: 95, 85, 75, 65, 55, 45, 35, 25, 15, 5 Grades assigned: A, B, B, B, C, C, C, D, D, F

Understanding curves

Key facts:
  • Flat curves are fairest when everyone took the same exam and one question was unfair.
  • Scaled curves assume the class performed predictably; they don't change relative rankings.
  • Square-root curves give more help to lower scores without punishing top performers as much.
  • Percentile curves enforce a fixed grade distribution regardless of absolute scores (e.g. "top 10% always get A").

Why curves happen

  • The exam was harder than expected and the class average is very low.
  • An exam question was ambiguous or had an error.
  • The instructor wants to ensure a natural spread of grades across letter bands.
  • External circumstances (fire alarm, tech failure) affected student performance.

What real curves are NOT

Curves are not grade inflation, make-up work, or second chances. Your instructor decides the method, not you. This tool is for exploring scenarios, not predicting your final grade.

Frequently asked questions

What is the difference between these curve methods?

Flat curves add the same points to everyone. Scaled curves change the scale so the top score becomes 100. Square-root curves are gentler and help lower scores more. Percentile curves ignore absolute scores and assign grades by rank. Your instructor picks one (if any).

Does my class have a curve?

Check your syllabus or ask your instructor. Many classes do not use curves. If your instructor says they will curve, they will specify which method.

Will this tool predict my exact grade?

No. This tool assumes every student's score gets treated equally. Real curves can be more nuanced: your instructor might curve only part of the grade, apply different methods to different parts, or use criteria you don't know about. Use this to understand how curves work, not to predict outcomes.

Can I paste in a list of scores?

Not yet — you'll need to enter them by hand or copy them one at a time. Each score must be 0–100.

Do curves guarantee a passing grade?

No. A curve shifts all scores up or redistributes them, but if the entire class performed poorly, a curve might only bring the average up slightly. Your instructor's curve (if applied) is final.

Why does this tool exist?

To help students understand how grading curves work mathematically. Many students wonder "if the class gets curved, what would my grade become?" This tool lets you explore that question safely without predicting your real grade.

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