{
  "id": "bmi",
  "version": "dc0e1768df38",
  "status": "published",
  "name": "BMI Calculator",
  "question": "What is my BMI?",
  "summary": "Computes body mass index (weight in kilograms divided by height in metres squared) and its CDC adult category, or the weight or height that gives a chosen BMI.",
  "category": "health",
  "subcategory": "body",
  "url": "https://www.acalculator.org/health/bmi-calculator",
  "markdown": "https://www.acalculator.org/health/bmi-calculator.md",
  "kind": "formulas",
  "method": "BMI = weight ÷ height², with weight in kilograms and height in metres (CDC).",
  "assumptions": [
    "The categories are the CDC adult categories, for people aged 20 and older. Children and teens use BMI-for-age percentiles instead.",
    "BMI is a screening measure. It does not measure body fat directly and does not diagnose health.",
    "The category is read from the BMI rounded to one decimal place, as shown: 18.5 to 24.9 is healthy weight, so 24.96 (rounded to 25.0, shown as 25) is overweight.",
    "The healthy weight range is the weights whose BMI shows as 18.5 to 24.9 at your height: BMI 18.45 to just under 24.95."
  ],
  "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,
        "maximum": 3
      },
      "weight": {
        "title": "Weight",
        "description": "Your body weight.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "mass",
        "exclusiveMinimum": 0,
        "maximum": 700
      },
      "bmi": {
        "title": "BMI",
        "description": "Body mass index: weight in kilograms divided by height in metres squared.",
        "type": "number",
        "exclusiveMinimum": 0,
        "maximum": 150
      }
    }
  },
  "solve": {
    "fillAny": 2,
    "variables": [
      "height",
      "weight",
      "bmi"
    ],
    "inputsOnly": []
  },
  "outputs": {
    "height": {
      "label": "Height",
      "description": "Your height without shoes.",
      "format": "quantity"
    },
    "weight": {
      "label": "Weight",
      "description": "Your body weight.",
      "format": "quantity"
    },
    "bmi": {
      "label": "Your BMI",
      "description": "Body mass index: weight in kilograms divided by height in metres squared.",
      "format": "number"
    },
    "category": {
      "label": "Category",
      "description": "The CDC adult BMI category: underweight, healthy weight, overweight, or obesity.",
      "format": "text"
    },
    "healthyMin": {
      "label": "Healthy weight from",
      "description": "The lowest weight whose BMI shows as 18.5 at this height: BMI 18.45 × height².",
      "format": "quantity",
      "unit": "lb"
    },
    "healthyMax": {
      "label": "Healthy weight up to",
      "description": "The weight at the top of the healthy range for this height: BMI 24.95 × height² (just under).",
      "format": "quantity",
      "unit": "lb"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "height": 1.778,
      "weight": 72.5747792
    },
    "outputs": {
      "bmi": 22.95737402903377,
      "category": "Healthy weight",
      "healthyMin": 58.3256898,
      "healthyMax": 78.8740358
    },
    "text": "At 160 lb, your BMI is 23, which is in the Healthy weight range for adults."
  },
  "examples": [
    {
      "given": {
        "weight": 68.0388555,
        "height": 1.651
      },
      "expect": {
        "bmi": 24.96,
        "category": "Overweight"
      },
      "source": "CDC English formula: 150 lb ÷ (65 in)² × 703 = 24.96 (weight and height given here in kg and m: 1 lb = 0.45359237 kg, 1 in = 0.0254 m); rounded to 25.0, overweight in the NHLBI one-decimal table (25.0 to 29.9)",
      "tolerance": 0.0005
    },
    {
      "given": {
        "weight": 70,
        "height": 1.75
      },
      "expect": {
        "bmi": 22.857142857142858,
        "healthyMin": 56.503125,
        "healthyMax": 76.409375
      },
      "source": "hand calculation in content.mdx: 70 ÷ 1.75² = 22.86; 18.45 × 1.75² = 56.50 kg; 24.95 × 1.75² = 76.41 kg"
    },
    {
      "given": {
        "bmi": 18.5,
        "height": 1.7526
      },
      "expect": {
        "weight": 56.82472505999999
      },
      "source": "CDC adult BMI categories: at 5 ft 9 in, 125 lb is the start of the healthy range; 18.5 × 1.7526² = 56.82 kg = 125.3 lb (hand calculation in content.mdx)"
    },
    {
      "given": {
        "weight": 90,
        "bmi": 30
      },
      "expect": {
        "height": 1.7320508075688772,
        "category": "Obesity"
      },
      "source": "hand calculation in content.mdx: height = √(90 ÷ 30) = √3 = 1.732 m; BMI 30 is obesity (CDC)"
    }
  ],
  "sources": [
    "Centers for Disease Control and Prevention, Adult BMI Categories. https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html",
    "Centers for Disease Control and Prevention, Adult BMI Calculator. https://www.cdc.gov/bmi/adult-calculator/index.html",
    "Centers for Disease Control and Prevention, Growth Chart Training, Calculating BMI Using the English System (weight ÷ height² × 703). https://www.cdc.gov/growth-chart-training/hcp/using-bmi/calculating-bmi.html",
    "National Heart, Lung, and Blood Institute, Calculate Your Body Mass Index (BMI categories to one decimal: underweight below 18.5, healthy 18.5 to 24.9, overweight 25.0 to 29.9, obesity 30.0 or above). https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm",
    "NIST SP 811 (2008), Appendix B: 1 lb = 0.45359237 kg and 1 in = 0.0254 m exactly."
  ],
  "related": [],
  "changelog": [
    {
      "date": "2026-09-28",
      "note": "The category is read from the BMI rounded to one decimal, as shown (24.96 rounds to 25.0 and is overweight); the healthy range is BMI 18.45 to just under 24.95."
    }
  ]
}