# Percent error calculator

- Human page: https://happytails.ai/en/calculators/percent-error/
- Markdown: https://happytails.ai/en/calculators/percent-error.md
- Structured JSON: https://happytails.ai/agents/en/calculators/percent-error/index.json
- Visibility: public

## Tool capabilities

| Property | Value |
| --- | --- |
| Tool ID | `percent-error` |
| Category | calculators |
| Implementation | Registered implementation. Registration alone is not a production-quality guarantee. |
| Browser execution | Automatic updates after valid input or file selection. |
| Browser processing | Browser; see tool notes for network behavior. |
| HTTP API | Not callable through HTTP. |
| Browser-agent interface | run_current_tool |

### Implementation notes

Absolute percent error = |measured - accepted| / |accepted| × 100. The signed result shows whether the measurement is higher or lower. The accepted value must be nonzero; both values are limited to magnitude 1 trillion.

### Inputs and settings

No free-text input is required. Use the file inputs and/or settings below.

| Setting | Meaning | Control type | Default | Constraints |
| --- | --- | --- | --- | --- |
| `measured` | Measured value | number | 9.5 | step=any |
| `accepted` | Accepted value | number | 10 | step=any |

### Browser-agent workflow

1. Open the human page in a browser that supports WebMCP.
2. Discover the interface exposed by that page; use its actual schema.
3. Select files on the page first when the tool requires files.
4. Call `run_current_tool` with valid input and settings.
5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links.

Calls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution.

### Planning specification

Percent error divides the absolute difference by the absolute reference value, then multiplies by 100. A zero reference is undefined and is rejected. Negative references are supported. Both inputs are limited to magnitude 1 trillion; use Percentage difference to compare two values without a reference.

This describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support.

### Complete machine-readable capability record

```json
{
  "id": "percent-error",
  "category": "calculators",
  "built": true,
  "requirements": "Percent error divides the absolute difference by the absolute reference value, then multiplies by 100. A zero reference is undefined and is rejected. Negative references are supported. Both inputs are limited to magnitude 1 trillion; use Percentage difference to compare two values without a reference.",
  "implementation": {
    "fields": [
      {
        "key": "measured",
        "label": "Measured value",
        "value": 9.5,
        "type": "number",
        "step": "any"
      },
      {
        "key": "accepted",
        "label": "Accepted value",
        "value": 10,
        "type": "number",
        "step": "any"
      }
    ],
    "input": false,
    "live": true,
    "presentation": "metrics",
    "note": "Absolute percent error = |measured - accepted| / |accepted| × 100. The signed result shows whether the measurement is higher or lower. The accepted value must be nonzero; both values are limited to magnitude 1 trillion.",
    "experience": {
      "automatic": true,
      "single": false,
      "inputMaxLength": 1000000,
      "inputMode": "text",
      "label": "Your text",
      "placeholder": "Type or paste your input…",
      "help": "Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.",
      "action": null
    },
    "mode": "automatic",
    "interactive": false
  },
  "execution": "Browser interface",
  "api": null,
  "browser_agent": {
    "supported": true,
    "name": "run_current_tool",
    "discovery": "WebMCP on the human page in a supporting browser",
    "verification": "See audit/API-AUDIT.md; availability is not verification"
  }
}
```

## Page guide

Compare a measurement with an accepted value and see the size and direction of its error.

How can we improve this tool?

Report a problem or share an idea.

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### How to use Percent error calculator

1. Enter the measured value and the accepted reference in the same units. The main percent error is nonnegative. The signed result shows whether the measurement is higher or lower than the reference.
2. A measurement of 9.5 against an accepted value of 10 has an absolute error of 0.5 and a percent error of 5%. Its signed percent error is -5%.

## Useful next steps

- [Percentage difference calculator](https://happytails.ai/en/calculators/percentage-difference/) ([Markdown](https://happytails.ai/en/calculators/percentage-difference.md))

- [Percentage change](https://happytails.ai/en/calculators/percentage-change/) ([Markdown](https://happytails.ai/en/calculators/percentage-change.md))

- [Rounding](https://happytails.ai/en/calculators/rounding/) ([Markdown](https://happytails.ai/en/calculators/rounding.md))

## Compare measured and accepted values

Enter the measured value and the accepted reference in the same units. The main percent error is nonnegative. The signed result shows whether the measurement is higher or lower than the reference.

### Try a small example

A measurement of 9.5 against an accepted value of 10 has an absolute error of 0.5 and a percent error of 5%. Its signed percent error is -5%.

### What to know

Percent error divides the absolute difference by the absolute reference value, then multiplies by 100. A zero reference is undefined and is rejected. Negative references are supported. Both inputs are limited to magnitude 1 trillion; use Percentage difference to compare two values without a reference.