{
  "id": "reverse-bmi",
  "version": "6af94e473c6a",
  "status": "published",
  "name": "Reverse BMI Calculator",
  "question": "Reverse BMI: what weight gives it?",
  "summary": "Works BMI backwards: the body weight that gives a chosen BMI at your height (BMI × height²), the healthy weight range for that height, and how far a current weight is from it.",
  "category": "health",
  "subcategory": "body",
  "url": "https://www.acalculator.org/health/reverse-bmi-calculator",
  "markdown": "https://www.acalculator.org/health/reverse-bmi-calculator.md",
  "kind": "function",
  "method": "Weight = BMI × height² (kg and m); in US units, weight (lb) = BMI × height (in)² ÷ 703.",
  "assumptions": [
    "Adults aged 20 and older; children and teens use BMI-for-age percentiles instead.",
    "The CDC adult categories: underweight below 18.5, healthy 18.5 to below 25, overweight 25 to below 30, obesity 30 or more.",
    "BMI is a screening measure; it does not measure body fat directly."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "height": {
        "title": "Height",
        "description": "Your height without shoes.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "exclusiveMinimum": 0.5,
        "maximum": 2.75
      },
      "bmi": {
        "title": "Target BMI",
        "description": "The body mass index you want the weight for; 18.5 to below 25 is the CDC healthy range.",
        "type": "number",
        "minimum": 10,
        "maximum": 80
      },
      "now": {
        "title": "Current weight",
        "description": "Optional: your weight now, to see how much it is from the target.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "mass",
        "minimum": 10,
        "maximum": 500
      }
    }
  },
  "outputs": {
    "weight": {
      "label": "Weight at this BMI",
      "description": "Target BMI × height², in kilograms or pounds.",
      "format": "quantity",
      "unit": "lb"
    },
    "category": {
      "label": "BMI category",
      "description": "The CDC adult category of the target BMI.",
      "format": "text"
    },
    "healthyMin": {
      "label": "Healthy weight from",
      "description": "BMI 18.5 × height²: the lowest weight in the CDC healthy range.",
      "format": "quantity",
      "unit": "lb"
    },
    "healthyMax": {
      "label": "Healthy weight below",
      "description": "BMI 25 × height²: the healthy range ends just below this weight.",
      "format": "quantity",
      "unit": "lb"
    },
    "change": {
      "label": "Change to reach it",
      "description": "Target weight − current weight: positive is a gain, negative a loss.",
      "format": "quantity",
      "unit": "lb"
    },
    "currentBmi": {
      "label": "Current BMI",
      "description": "Current weight ÷ height².",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "bmi": 22,
      "height": 1.7526
    },
    "outputs": {
      "weight": 67.57534872,
      "category": "Healthy weight",
      "healthyMin": 56.82472506,
      "healthyMax": 76.790169
    },
    "text": "At 5 ft 9 in, a BMI of 22 is a weight of 149 lb."
  },
  "examples": [
    {
      "given": {
        "height": 1.75,
        "bmi": 22
      },
      "expect": {
        "weight": 67.375,
        "category": "Healthy weight",
        "healthyMin": 56.65625,
        "healthyMax": 76.5625
      },
      "source": "CDC, Adult BMI Categories: BMI = weight (kg) ÷ height (m)²; underweight below 18.5, healthy weight 18.5 to below 25, overweight 25 to below 30, obesity 30 or more, https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html (retrieved 2026-10-05); hand calculation in content.mdx: 22 × 1.75² = 67.375 kg; 18.5 × 3.0625 = 56.65625 kg; 25 × 3.0625 = 76.5625 kg"
    },
    {
      "given": {
        "height": 1.7526,
        "bmi": 25,
        "now": 81.6466266
      },
      "expect": {
        "weight": 76.79016899999999,
        "category": "Overweight",
        "change": -4.856457600000013
      },
      "source": "CDC, Adult BMI Categories: BMI = weight (kg) ÷ height (m)²; underweight below 18.5, healthy weight 18.5 to below 25, overweight 25 to below 30, obesity 30 or more, https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html (retrieved 2026-10-05); hand calculation in content.mdx: 25 × 69² ÷ 703 = 169.3 lb (CDC English formula), so 10.7 lb to lose; in kg 25 × 1.7526² = 76.789 kg",
      "tolerance": 1e-9
    },
    {
      "given": {
        "height": 1.6256,
        "bmi": 18.5,
        "now": 45.359237
      },
      "expect": {
        "weight": 48.88764416,
        "category": "Healthy weight",
        "currentBmi": 17.164784659159164
      },
      "source": "CDC, Adult BMI Categories: BMI = weight (kg) ÷ height (m)²; underweight below 18.5, healthy weight 18.5 to below 25, overweight 25 to below 30, obesity 30 or more, https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html (retrieved 2026-10-05); hand calculation in content.mdx: 18.5 × 1.6256² = 48.888 kg = 107.8 lb; 100 lb is BMI 17.2"
    }
  ],
  "sources": [
    "Centers for Disease Control and Prevention. Adult BMI Categories, retrieved 2026-10-05. https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html",
    "Centers for Disease Control and Prevention. Body Mass Index (BMI): the formula, kg/m² and 703 × lb/in², retrieved 2026-10-05. https://www.cdc.gov/bmi/faq/index.html",
    "NIST Special Publication 811, Appendix B: 1 lb = 0.45359237 kg and 1 in = 2.54 cm exactly, retrieved 2026-10-05. https://www.nist.gov/pml/special-publication-811"
  ],
  "related": [
    "ideal-weight",
    "weight-loss",
    "bmr"
  ],
  "changelog": []
}