# Body Fat Percentage Calculator API

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

Estimate body fat percentage with the US Navy method and age-adjusted healthy ranges.

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

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

## Endpoint

`POST https://api.miniwebtool.com/v1/tools/body-fat-percentage-calculator/run`

## Request body

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `gender` | `str` | yes | male | female Choices: male, female |
| `height` | `float` | yes |  |
| `neck` | `float` | yes |  |
| `waist` | `float` | yes |  |
| `hip` | `float | None` | no |  |
| `unit_system` | `str` | no | metric | imperial Choices: metric, imperial |
| `age` | `int` | no |  |

## Example request

```json
{
  "gender": "male",
  "height": 178,
  "neck": 38,
  "waist": 85,
  "unit_system": "metric"
}
```

## cURL

```bash
curl -X POST https://api.miniwebtool.com/v1/tools/body-fat-percentage-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"gender":"male","height":178,"neck":38,"waist":85,"unit_system":"metric"}'
```

## Response envelope

```json
{
  "request_id": "01K...",
  "tool": "body-fat-percentage-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 Body Fat Percentage Calculator API do?

Estimate body fat percentage with the US Navy method and age-adjusted healthy ranges. 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: gender, height, neck, waist. Full schema at `https://api.miniwebtool.com/v1/openapi.json`.

### Is this deterministic?

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