# Body Fat Calculator — REST API endpoint `body-fat-calculator`

Estimate body fat percentage, fat mass, lean mass, BMI, and a body-composition category. Uses the U.S. Navy circumference method (waist, neck, hip) or a BMI-based estimate (Deurenberg formula). Metric (kg/cm) or imperial (lbs/in) inputs.

- Category: calculators
- MCP server: https://mcp.findutils.com/ (Streamable HTTP, no API keys, 120 req/min per IP)
- REST endpoint: POST https://api.findutils.com/api/tools/body-fat-calculator/execute (no API keys, 60 req/min per IP)
- Reference page: https://findutils.com/api/body-fat-calculator/
- Same tool on the other surface: https://findutils.com/mcp/body-fat-calculator/

## Call the endpoint (verified example)

```bash
curl -X POST https://api.findutils.com/api/tools/body-fat-calculator/execute \
  -H "Content-Type: application/json" \
  -d '{
    "gender": "male",
    "weight": 70,
    "height": 175,
    "waist": 85,
    "neck": 38
  }'

# Parameter schema
curl https://api.findutils.com/api/tools/body-fat-calculator
```

## Input schema

| Argument | Type | Required | Description |
|---|---|---|---|
| `gender` | string (male \| female) | yes | Biological sex used by the formulas. |
| `weight` | number | yes | Body weight in kg (metric) or lbs (imperial). |
| `height` | number | yes | Height in cm (metric) or inches (imperial). |
| `unit_system` | string (metric \| imperial) | no | Unit system for all measurements. Default: `"metric"`. |
| `method` | string (navy \| bmi) | no | "navy" = U.S. Navy circumference method (needs waist, neck, and hip for female). "bmi" = BMI-based estimate. Default: `"navy"`. |
| `waist` | number | no | Waist circumference at the navel (cm or in). Required for the navy method. |
| `neck` | number | no | Neck circumference below the larynx (cm or in). Required for the navy method. |
| `hip` | number | no | Hip circumference at the widest point (cm or in). Required for the navy method when gender is female. |
| `age` | integer | no | Age in years. Only used by the bmi method. Default 30. Default: `30`. |

Example arguments (verified):

```json
{
  "gender": "male",
  "weight": 70,
  "height": 175,
  "waist": 85,
  "neck": 38
}
```

OpenAPI 3.1 spec: https://findutils.com/api/openapi.json · Interactive docs: https://findutils.com/api/docs/

## Also an MCP tool

```bash
claude mcp add findutils --transport http https://mcp.findutils.com/
```

Then ask the client to call `findutils:body_fat_calculator`. Full MCP reference: https://findutils.com/mcp/body-fat-calculator/

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