# Roman numeral converter

- Human page: https://happytails.ai/en/education-tools/roman-numeral-converter/
- Markdown: https://happytails.ai/en/education-tools/roman-numeral-converter.md
- Structured JSON: https://happytails.ai/agents/en/education-tools/roman-numeral-converter/index.json
- Visibility: public

## Tool capabilities

| Property | Value |
| --- | --- |
| Tool ID | `roman-numeral-converter` |
| Category | education-tools |
| 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

Converts both ways using standard subtractive Roman numerals from 1 to 3,999. Zero, negative numbers, decimals and overbar notation are not supported.

### Inputs and settings

Text input: Number or Roman numeral.

Example or placeholder shown in the interface (not a validated fixture):

```text
2026
```

Enter 1 to 3999, or a standard Roman numeral such as MMXXVI. Results update as you type. Up to 1,000,000 characters.

No additional settings are declared for this tool.

### 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

Zero, negative numbers, decimals and overbar notation are outside this tool's range. Nonstandard strings such as IIII and IC are rejected instead of guessed.

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

### Complete machine-readable capability record

```json
{
  "id": "roman-numeral-converter",
  "category": "education-tools",
  "built": true,
  "requirements": "Zero, negative numbers, decimals and overbar notation are outside this tool's range. Nonstandard strings such as IIII and IC are rejected instead of guessed.",
  "implementation": {
    "fields": [],
    "live": true,
    "presentation": "metrics",
    "note": "Converts both ways using standard subtractive Roman numerals from 1 to 3,999. Zero, negative numbers, decimals and overbar notation are not supported.",
    "experience": {
      "automatic": true,
      "single": true,
      "inputMaxLength": 1000000,
      "inputMode": "text",
      "label": "Number or Roman numeral",
      "placeholder": "2026",
      "help": "Enter 1 to 3999, or a standard Roman numeral such as MMXXVI. 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

Convert numbers to Roman numerals. Or the other way round.

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 Roman numeral converter

1. Enter number or roman numeral in the input field.
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

- [Number to words](https://happytails.ai/en/text-tools/number-to-words/) ([Markdown](https://happytails.ai/en/text-tools/number-to-words.md))

- [Number base converter](https://happytails.ai/en/developer-tools/number-base-converter/) ([Markdown](https://happytails.ai/en/developer-tools/number-base-converter.md))

- [Scientific calculator](https://happytails.ai/en/calculators/scientific-calculator/) ([Markdown](https://happytails.ai/en/calculators/scientific-calculator.md))

## How to use it

Enter a whole number from 1 to 3,999 or a standard Roman numeral. Both directions work in the same input, including lowercase Roman letters.

### A worked example

2026 becomes MMXXVI. XLII becomes 42. Subtractive pairs such as IV, IX, XL and CM are accepted.

### What to know

Zero, negative numbers, decimals and overbar notation are outside this tool's range. Nonstandard strings such as IIII and IC are rejected instead of guessed.