# Empirical Formula Calculator API

> For the complete documentation index, see [llms.txt](/llms.txt).

Empirical formula from element mass percentages or masses, with optional molecular formula when a molecular mass is supplied.

Use this endpoint to add the tool to your app, site, workflow, or agent without rebuilding formulas, validation, examples, and docs.

- Slug: `empirical-formula-calculator`
- Category: `science`
- Version: `2026-04-22`
- Credits per successful call: 1
- Starts on: free
- Max payload: 65536 bytes
- Privacy mode: `no_body_logs`
- Available on: free, starter, pro, business, scale
- Browser tool: https://miniwebtool.com/empirical-formula-calculator/

## Endpoint

`POST https://api.miniwebtool.com/v1/tools/empirical-formula-calculator/run`

## Request body

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `elements` | `str` | no | comma-separated element symbols, e.g. C,H,O |
| `values` | `str` | no | comma-separated mass or percentage values matching elements |
| `mode` | `str` | no | percentage | mass Choices: percentage, mass |
| `molecular_mass` | `float | None` | no | optional molecular mass to also derive the molecular formula |

## Example request

```json
{
  "elements": "C,H,O",
  "values": "40.0,6.7,53.3",
  "mode": "percentage"
}
```

## cURL

```bash
curl -X POST https://api.miniwebtool.com/v1/tools/empirical-formula-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"elements":"C,H,O","values":"40.0,6.7,53.3","mode":"percentage"}'
```

## Response envelope

```json
{
  "request_id": "01K...",
  "tool": "empirical-formula-calculator",
  "tool_version": "2026-04-22",
  "credits_used": 1,
  "result": {}
}
```

## Errors

Errors are RFC 7807 `application/problem+json`. Branch on `code`, not `title`.

## MCP

Agents can discover and call this tool through `https://api.miniwebtool.com/mcp` or `https://api.miniwebtool.com/v1/mcp` using MCP `tools/list` and `tools/call`.

## Frequently asked

### What does the Empirical Formula Calculator API do?

Empirical formula from element mass percentages or masses, with optional molecular formula when a molecular mass is supplied. Use it to add this utility without rebuilding formulas, validation, examples, and documentation.

### How much does one call cost?

1 credit per successful call. Failed calls do not bill.

### What parameters are required?

Required fields: (none). Full schema at `https://api.miniwebtool.com/v1/openapi.json`.

### Is this deterministic?

Yes. Same input, same output. Tool version: 2026-04-22.