# Percentage difference calculator

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

## Tool capabilities

| Property | Value |
| --- | --- |
| Tool ID | `percentage-difference` |
| 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

For two nonnegative values: absolute difference divided by their average, times 100. This is symmetric; use Percentage change when one value is the original. Two zeros give 0%.

### Inputs and settings

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

| Setting | Meaning | Control type | Default | Constraints |
| --- | --- | --- | --- | --- |
| `a` | First value | number | 100 | min=0 max=1e+100 step=any |
| `b` | Second value | number | 120 | min=0 max=1e+100 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

Percentage difference treats both values equally. Percentage change uses an original value as its denominator. Use the separate Percentage change tool for growth or decline over time. Two zero values return 0%.

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

### Complete machine-readable capability record

```json
{
  "id": "percentage-difference",
  "category": "calculators",
  "built": true,
  "requirements": "Percentage difference treats both values equally. Percentage change uses an original value as its denominator. Use the separate Percentage change tool for growth or decline over time. Two zero values return 0%.",
  "implementation": {
    "fields": [
      {
        "key": "a",
        "label": "First value",
        "value": 100,
        "type": "number",
        "min": 0,
        "max": 1e+100,
        "step": "any"
      },
      {
        "key": "b",
        "label": "Second value",
        "value": 120,
        "type": "number",
        "min": 0,
        "max": 1e+100,
        "step": "any"
      }
    ],
    "input": false,
    "live": true,
    "presentation": "metrics",
    "note": "For two nonnegative values: absolute difference divided by their average, times 100. This is symmetric; use Percentage change when one value is the original. Two zeros give 0%.",
    "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 two values without picking a starting point.

How can we improve this tool?

Report a problem or share an idea.

Please leave out private information. Your message and the tool name go to our team via PostHog.

### How to use Percentage difference calculator

1. Enter the values you want to calculate and choose the relevant units or settings.
2. The result updates as you type. Adjust the available settings if needed.
3. Review the result, then use Copy result or a download link when available.

## Useful next steps

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

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

- [Discount](https://happytails.ai/en/calculators/discount/) ([Markdown](https://happytails.ai/en/calculators/discount.md))

## How to use it

Enter two nonnegative values. The percentage difference is their absolute difference divided by their average, multiplied by 100.

### A worked example

For 100 and 120, the difference is 20 and the average is 110. The percentage difference is 18.1818%. Swapping the two values gives the same answer.

### What to know

Percentage difference treats both values equally. Percentage change uses an original value as its denominator. Use the separate Percentage change tool for growth or decline over time. Two zero values return 0%.