{
  "schemaVersion": 1,
  "slug": "one-rep-max-calculator",
  "category": "health",
  "kind": "implementation",
  "independentValidation": false,
  "implementationHash": "8d401b41a79716840ed508a0257dc3a77eba4ac1babf4affa17a6d6fa5f0363a",
  "provenance": "Generated from the calculation contract used by the published page. Publication is not external validation.",
  "sourceFiles": [
    "data/calculators/one-rep-max-calculator.json",
    "src/engine.js"
  ],
  "runtimeSource": "/sources/engine.txt",
  "runtimeHash": "5c888d8898afbdee36267bb9977829e1e2ac568f6677c8ee87469c139864645c",
  "scope": "The compute function records implemented equations, constants, lookup tables and custom rules. Inputs record defaults and allowed values; outputs record precision and units. Defaults are examples, not recommendations. General background references are not evidence for this specific algorithm.",
  "publishedFormula": {
    "formula": "1RM = W × ((1+r/30) + 36/(37−r) + r^0.10)/3",
    "vars": [
      [
        "1RM",
        "estimated one-rep max (average)"
      ],
      [
        "W",
        "weight lifted"
      ],
      [
        "r",
        "reps performed"
      ]
    ],
    "note": "Mean of Epley W(1+r/30), Brzycki W×36/(37−r) and Lombardi W×r^0.10; 90% estimate = 0.9×1RM."
  },
  "externalEvidence": {
    "reviewedAt": "2026-10-12",
    "sources": [
      {
        "name": "Brzycki (1993) — Strength testing and predicted 1RM",
        "url": "https://doi.org/10.1080/07303084.1993.10606684"
      }
    ],
    "referenceRole": "context",
    "implementationHash": "8d401b41a79716840ed508a0257dc3a77eba4ac1babf4affa17a6d6fa5f0363a",
    "basis": "1RM = W × ((1+r/30) + 36/(37−r) + r^0.10)/3",
    "limitations": "The references provide context and limitations. They do not validate this page’s illustrative multipliers, lookup values or predictions."
  },
  "contract": {
    "compute": "const epley = weight*(1+reps/30); const brzycki = weight*(36/(37-reps)); const lombardi = weight*Math.pow(reps, 0.10); const avg = (epley+brzycki+lombardi)/3; return { epley, brzycki, lombardi, average: avg, percent90: avg*0.9 };",
    "inputs": [
      {
        "name": "weight",
        "type": "number",
        "default": 100,
        "min": 0,
        "max": 1000,
        "step": 0.5,
        "slider": true
      },
      {
        "name": "reps",
        "type": "number",
        "default": 5,
        "min": 1,
        "max": 20,
        "step": 1,
        "slider": true
      }
    ],
    "outputs": [
      {
        "name": "epley",
        "precision": 1,
        "unit": "kg"
      },
      {
        "name": "brzycki",
        "precision": 1,
        "unit": "kg"
      },
      {
        "name": "lombardi",
        "precision": 1,
        "unit": "kg"
      },
      {
        "name": "average",
        "precision": 1,
        "unit": "kg"
      },
      {
        "name": "percent90",
        "precision": 1,
        "unit": "kg"
      }
    ],
    "interpret": null
  }
}