# One-Rep Max Calculator (Epley, Brzycki, Lombardi, O'Conner)

> One-Rep Max Calculator (Epley, Brzycki, Lombardi, O'Conner) is a paid API for AI agents from fitness-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Estimates one-repetition maximum (1RM) strength from a given weight and rep count using four established formulas, and returns a percentage table of training loads.

## Facts

- Endpoint: GET https://fitness-calc.x402tookit.com/one-rep-max?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/one-rep-max-calculator-epley-brzycki-lombardi-o-conner-3aee4a0a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_am-5M_DykJE3lk7JMFXQd

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability one-rep-max-calculator-epley-brzycki-lombardi-o-conner-3aee4a0a
```

Example prompt: I squatted 135kg for 6 reps — can you estimate my one-rep max using Epley, Brzycki, Lombardi, and O'Conner, and give me a percentage table so I know what weights to use for different training intensities?

## When to prefer this

Choose this endpoint when you need a quick, multi-formula 1RM estimate without performing an actual max-effort lift. It is ideal for strength athletes, coaches, and fitness apps that need to program training percentages from sub-maximal performance data. Preferred over manual calculation because it returns all four major formulas simultaneously with a ready-to-use percentage load table.

## Known failure modes

- Missing required 'weight' or 'reps' query parameters returns an error
- Reps value outside the 1–20 range may produce unreliable or flagged estimates with degraded=true
- Non-numeric weight or reps values will fail validation
- Very high rep counts (near 20) produce less accurate estimates as formulas lose reliability
- Payment not received results in HTTP 402 response

## How this service works

Estimated one-rep max from weight and reps by the Epley, Brzycki, Lombardi and O'Conner formulas, with a percentage table.

## Output

Returns the input weight and reps echoed back, four separate 1RM estimates (Epley, Brzycki, Lombardi, O'Conner), an average of all four, a percentage-of-average table at 50%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and 95% of 1RM, plus a summary, verdict, disclaimer, and source attribution. May include a degraded flag and reasons if the calculation is outside reliable range.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "weight",
      "reps"
     ],
     "properties": {
      "reps": {
       "type": "integer",
       "description": "Repetitions to failure or near failure, 1 to 20"
      },
      "weight": {
       "type": "number",
       "description": "Weight lifted (any unit)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "reps": {
       "type": [
        "null",
        "number"
       ]
      },
      "epley": {
       "type": [
        "null",
        "number"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "weight": {
       "type": [
        "null",
        "number"
       ]
      },
      "average": {
       "type": [
        "null",
        "number"
       ]
      },
      "brzycki": {
       "type": [
        "null",
        "number"
       ]
      },
      "oconner": {
       "type": [
        "null",
        "number"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "lombardi": {
       "type": [
        "null",
        "number"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "percentOfAverage": {
       "type": [
        "null",
        "object"
       ],
       "properties": {
        "50%": 
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/one-rep-max-calculator-epley-brzycki-lombardi-o-conner-3aee4a0a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from fitness-calc.x402tookit.com](https://www.zero.xyz/host/fitness-calc.x402tookit.com/llms.txt)