# One Rep Max Calculator — MCP tool `findutils:one_rep_max_calculator`

Estimate a one-rep max (1RM) from a weight lifted for a number of reps, using Brzycki, Epley, Lander, Lombardi, Mayhew, O'Conner, and Wathen formulas. Returns the chosen formula result, every formula result, and a training-weight table (100% to 60%) with rep ranges and zones.

- 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/one-rep-max-calculator/execute (no API keys, 60 req/min per IP)
- Reference page: https://findutils.com/mcp/one-rep-max-calculator/
- Same tool on the other surface: https://findutils.com/api/one-rep-max-calculator/

## Connect

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

Claude Desktop (`claude_desktop_config.json`):

```json
{
  "mcpServers": {
    "findutils": {
      "url": "https://mcp.findutils.com/"
    }
  }
}
```

## Call the tool (verified example)

```bash
curl -X POST https://mcp.findutils.com/ \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
      "name": "one_rep_max_calculator",
      "arguments": {
        "weight": 100,
        "reps": 5
      }
    }
  }'
```

## Input schema

| Argument | Type | Required | Description |
|---|---|---|---|
| `weight` | number | yes | Weight lifted, in the chosen unit. |
| `reps` | integer | yes | Reps performed with that weight (1-30). |
| `unit` | string (kg \| lbs) | no | Weight unit, echoed back in the result. Default: `"kg"`. |
| `formula` | string (brzycki \| epley \| lander \| lombardi \| mayhew \| oconner \| wathen) | no | Formula used for the headline one_rep_max. Default: `"brzycki"`. |

Example arguments (verified):

```json
{
  "weight": 100,
  "reps": 5
}
```

## Also a REST endpoint

```bash
curl -X POST https://api.findutils.com/api/tools/one-rep-max-calculator/execute \
  -H "Content-Type: application/json" \
  -d '{
    "weight": 100,
    "reps": 5
  }'

# Parameter schema
curl https://api.findutils.com/api/tools/one-rep-max-calculator
```

Full REST reference: https://findutils.com/api/one-rep-max-calculator/ · OpenAPI 3.1 spec: https://findutils.com/api/openapi.json

---
Full catalog: POST https://mcp.findutils.com/ with method `tools/list` · https://findutils.com/mcp/ · https://findutils.com/llms.txt