{
  "slug": "one-rep-max",
  "title": "One Rep Max Calculator",
  "heading": "1RM Calculator",
  "category": "fitness-health",
  "url": "https://www.revenuelab.fyi/toolbox/one-rep-max",
  "summary": "Estimate your one rep max from a tested rep.",
  "description": "Uses the Epley and Brzycki formulas to estimate 1RM from a recent lift.",
  "formula": null,
  "dateModified": "2026-10-03",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=one-rep-max",
  "inputs": [
    {
      "id": "weight",
      "label": "Weight lifted",
      "kind": "number",
      "hint": null,
      "default": 185,
      "unit": "lb/kg",
      "min": 0,
      "max": null
    },
    {
      "id": "reps",
      "label": "Reps performed",
      "kind": "number",
      "hint": null,
      "default": 5,
      "unit": null,
      "min": 1,
      "max": 30
    }
  ],
  "outputs": [
    {
      "id": "avg",
      "label": "Estimated 1RM (avg)",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "epley",
      "label": "Epley formula",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "brzycki",
      "label": "Brzycki formula",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Weight lifted: 185 lb/kg",
      "Reps performed: 5"
    ],
    "outputs": [
      "Estimated 1RM (avg): 212",
      "Epley formula: 215.8",
      "Brzycki formula: 208.1"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter weight lifted (lb/kg).",
      "Enter reps performed.",
      "Read your estimated 1rm (avg) on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "weight": 185,
        "reps": 3
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "weight": 185,
        "reps": 5
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "weight": 185,
        "reps": 8
      }
    }
  ],
  "limitations": [
    "Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.",
    "Results do not account for medical conditions, medication, or pregnancy.",
    "Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it."
  ],
  "faq": [
    {
      "q": "How does the 1rm calculator work?",
      "a": "Uses the Epley and Brzycki formulas to estimate 1RM from a recent lift."
    },
    {
      "q": "What do I need to enter?",
      "a": "2 values: weight lifted, and reps performed. Each field starts with a sensible default, so you can change one number at a time and watch the result move."
    },
    {
      "q": "What does the estimated 1rm (avg) result mean?",
      "a": "It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds."
    },
    {
      "q": "Is this calculator free, and do I need an account?",
      "a": "Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser."
    },
    {
      "q": "How accurate is the result?",
      "a": "It applies the standard formula exactly, so the arithmetic is precise. Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass."
    },
    {
      "q": "Who is this tool for?",
      "a": "It's built for anyone tracking a health or training target and wanting the standard formula applied correctly, without a signup or an app."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/bmr",
    "https://www.revenuelab.fyi/toolbox/tdee"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — One Rep Max Calculator (https://www.revenuelab.fyi/toolbox/one-rep-max)"
}