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Free curve calculator for teachers

Grade Curve Calculator

Paste your class’s scores and try five ways to curve them — add points, top score to 100, a target average, a bell curve or the square root curve. See every new score and grade, then copy them back to your gradebook.

Curve

Curved scores

In the same order as you pasted them — paste straight back into your gradebook.

#OriginalCurvedChangeGrade

How to curve grades with this calculator

  1. Copy the score column from your spreadsheet or gradebook and paste it in. Scores like 18/20 work too.
  2. Pick a curve and set its target — points to add, target average, or average and spread for a bell curve.
  3. Check the new average and grade spread, then press Copy curved scores and paste them back.

Five ways to curve grades

Add points

Everyone gets the same number of points. Simple, and the order and gaps between students stay the same.

Top score to 100

Find how far the highest score is from 100 and add that to everyone. If the best student got 88, everyone gets 12 points. It is the most common curve in high school.

Set the class average

Shift every score by the same amount so the average lands where you want it — say 75 or 78.

Bell curve

new = target average + (score − class average) ÷ class SD × target SD

Scores are placed on a new distribution with the average and spread you choose. A smaller target spread pulls scores together, so it can lower the top scores unless you keep “Never lower a score” on.

Square root curve

new = 10 × √score

It lifts low scores the most — a 49 becomes 70 — while a 100 stays 100.

More tools for teachers

Grade a test from the number wrong with the Easy Grader, print a chart for any test length from the grading scale pages, or average weighted categories with the grade calculator.

Frequently asked questions

How do you curve grades?

The simplest way is to add the same number of points to every score — for example enough that the top score becomes 100. Other common curves set the class average to a target, rescale scores to a bell curve, or use the square root curve (10 × √score).

How does a bell curve work for grades?

Each score is turned into its distance from the class average in standard deviations, then placed the same distance from a new target average with a new spread. With a target average of 78 and spread of 10, a student one standard deviation above the class average ends at 88.

What is the square root curve?

Take the square root of each percent and multiply by 10. A 64 becomes 80, an 81 becomes 90 and a 100 stays 100. It helps low scores the most and never pushes anyone over 100.

Can a curve lower someone’s grade?

A bell curve can, because it squeezes scores toward the target. Keep “Never lower a score” on to make sure every student ends up at or above their original score.

Which curve is fairest?

Adding the same points (or top score to 100) keeps the gaps between students exactly the same, which is why most teachers use it. The square root curve helps struggling students more; a bell curve is common in large college classes that grade relative to the class.

Are the scores I paste stored anywhere?

Only in your browser on this device, so they are there when you come back. Nothing is uploaded, and the tool never asks for student names.