Grade Curve Calculator

By CalculatorBolt Team | Published: | Updated: | Reviewed by: Academic & Assessment Editor

Curve a set of scores to a target mean and spread in seconds. Add constants, scale, line up to a target mean, apply a bell‑curve (z‑score) transform, or map percentiles. Then bin results into A/B/C grades and export a final sheet. This is an informational tool—always follow your department's policy.

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Grade Curve Calculator

Scores Input

Enter scores, one per line or separated by commas
Remove N lowest scores

Curving Method

Output Options

Grade Binning Configuration

Grade Label Threshold Action

Visual Analysis

Score Distribution (Raw vs Curved)

Calculate curve to see histogram

Grade Distribution

Calculate curve to see grade distribution

Export Data

Import Configuration

Import a previously exported JSON configuration

How it works

Pick a method: add/scale, linear shift to a target mean, linear fit (mean & range), bell‑curve (z‑score to target μ, σ), or percentile mapping. We compute curved scores, clamp to your floor/cap, and round as chosen. Then, apply grade thresholds by score, percent, or percentile to label A/B/C bins.

Inputs explained

  • Scores input: paste scores or import a CSV with Name,Score. Drop lowest N and optionally winsorize outliers.
  • Methods: choose a transformation; set target mean/SD or anchors. Clamp and round outputs.
  • Grade Bins: pick threshold mode and labels; see live counts.
  • Export: CSV final sheet, JSON config; share link recreates your setup.

Example

Raw scores (N=8): 52, 61, 64, 68, 71, 75, 82, 88 → raw μ≈70.1, σ≈11.1

Bell‑curve to μt=75, σt=10:

  • z = (old − 70.1)/11.1; new = 75 + 10×z; clamp [0,100], round 0.1
  • Curved μ≈75.0, σ≈10.0 (values vary slightly after rounding/clamping)

Grade bins (threshold A≥85, B≥75, C≥65, D≥55, F<55):

Counts might be A:2, B:3, C:2, D:1, F:0 (illustrative)

Tips & notes

  • Always check institutional policy before curving (some require linear only; others ban adjusting relative ranks).
  • A bell‑curve transform assumes a roughly normal distribution; outliers can distort mean/SD—consider winsorizing first.
  • Percentile mapping preserves rank exactly and lets you target any curve via anchors.

FAQs

Follow your policy. Linear shift keeps spread; bell‑curve sets both mean and SD; percentile mapping preserves ranks while targeting a distribution.

Linear, z‑score, and percentile methods preserve order when monotonic; ties may remain ties depending on rounding.

Yes—use clamp options. You can also round to 0, 0.1, or 0.5 as needed.

Use fixed score thresholds (e.g., A≥90) or percent/percentile‑based bins (e.g., top 15% A).

No. Everything runs in your browser. Use Export or Share Link to save/share your configuration.

Disclaimer

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