{
  "slug": "ideal-body-weight",
  "title": "Ideal Body Weight Calculator (Devine Formula)",
  "heading": "Ideal Body Weight Calculator",
  "category": "fitness-health",
  "url": "https://www.revenuelab.fyi/toolbox/ideal-body-weight",
  "summary": "Devine formula IBW used for drug dosing and ventilator settings.",
  "description": "Ideal body weight (IBW) via the Devine formula is the reference weight clinicians use for weight-based drug dosing and mechanical ventilation tidal volume settings, because dosing many medications on actual body weight in an overweight or obese patient can meaningfully overdose the patient — lean tissue, not fat, drives distribution and clearance for many drugs. The Devine formula assigns a base weight for 5 feet of height and adds a fixed increment per inch over that, separately for men and women, reflecting average frame differences. It performs poorly for patients under 5 feet tall (may return negative or unrealistically low numbers) and does not account for large frame variation, so it is a dosing convention rather than a body-composition assessment. Ventilator tidal volume, for example, is set at roughly 6-8 mL per kg of IBW, not actual weight, because lung size tracks height and sex, not body fat. Many drug protocols specify whether to use IBW, adjusted body weight, or actual weight — check the specific drug reference. This tool is for education and workflow support only — not medical advice. Always verify results with a clinician and use clinical judgment alongside your institution's protocols.",
  "formula": "Men: IBW = 50 kg + 2.3 kg per inch over 60in. Women: IBW = 45.5 kg + 2.3 kg per inch over 60in.",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=ideal-body-weight",
  "inputs": [
    {
      "id": "heightIn",
      "label": "Height",
      "kind": "number",
      "hint": null,
      "default": 68,
      "unit": "in",
      "min": 48,
      "max": 84
    },
    {
      "id": "sex",
      "label": "Sex",
      "kind": "select",
      "hint": null,
      "default": "male",
      "options": [
        {
          "value": "male",
          "label": "Male"
        },
        {
          "value": "female",
          "label": "Female"
        }
      ]
    },
    {
      "id": "actualKg",
      "label": "Actual weight (optional, for comparison)",
      "kind": "number",
      "hint": null,
      "default": 90,
      "unit": "kg",
      "min": 20,
      "max": 300
    }
  ],
  "outputs": [
    {
      "id": "ibw",
      "label": "Ideal body weight",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "tidalVolLow",
      "label": "Tidal volume 6 mL/kg IBW",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "tidalVolHigh",
      "label": "Tidal volume 8 mL/kg IBW",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "percentIbw",
      "label": "Actual weight as % of IBW",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Height: 68 in",
      "Sex: Male",
      "Actual weight (optional, for comparison): 90 kg"
    ],
    "outputs": [
      "Ideal body weight: 68.4",
      "Tidal volume 6 mL/kg IBW: 410",
      "Tidal volume 8 mL/kg IBW: 547",
      "Actual weight as % of IBW: 132"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter height (in).",
      "Enter sex.",
      "Enter actual weight (optional, for comparison) (kg).",
      "Read your ideal body weight 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": {
        "heightIn": 48,
        "sex": "male",
        "actualKg": 54
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "heightIn": 68,
        "sex": "male",
        "actualKg": 90
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "heightIn": 84,
        "sex": "male",
        "actualKg": 144
      }
    }
  ],
  "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": "Why use IBW instead of actual weight for dosing?",
      "a": "Many drugs distribute mainly into lean tissue, water, or blood volume, none of which scale up proportionally with fat mass. Dosing an obese patient on actual body weight for these drugs can produce toxic concentrations, so protocols specify IBW, or a blend like adjusted body weight, to approximate the effective distribution volume more safely."
    },
    {
      "q": "What is IBW used for besides drug dosing?",
      "a": "Ventilator management is the other major use — tidal volume in lung-protective ventilation strategies is calculated from predicted body weight (essentially IBW) rather than actual weight, because lung volume correlates with height and sex, not with how much fat or muscle a patient carries."
    },
    {
      "q": "Does the Devine formula work for very short patients?",
      "a": "Not well. Below about 5 feet, the formula can produce very low or even negative values, which is a known limitation. For pediatric or unusually short adult patients, use age- and height-based pediatric weight references or clinical judgment instead."
    },
    {
      "q": "How is this different from adjusted body weight?",
      "a": "IBW alone underestimates dosing needs in obese patients for some drugs, since obese patients still have more lean mass than a person at ideal weight. Adjusted body weight adds a fraction of the excess weight above IBW back in in to better reflect that extra lean tissue — see the companion adjusted body weight calculator."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/adjusted-body-weight",
    "https://www.revenuelab.fyi/toolbox/creatinine-clearance-cockcroft-gault",
    "https://www.revenuelab.fyi/toolbox/total-daily-insulin-dose"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Ideal Body Weight Calculator (Devine Formula) (https://www.revenuelab.fyi/toolbox/ideal-body-weight)"
}