{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"bmi"},"result":{"entity_type":"calculator","id":"bmi","calculator_id":"bmi","canonical_url":"https://tttkmbb.com/health/bmi","name":"BMI Calculator","title":"BMI Calculator – Body Mass Index from Weight and Height (WHO categories)","category":"health","category_name":"Health","tool_name":"calculate_bmi","featured_mcp_tool":true,"description":"Computes body mass index (BMI) from weight and height and classifies it with the WHO adult categories, plus the healthy weight range for that height.","use_when":"You need an adult's BMI, its WHO/CDC weight category, or the weight range that corresponds to a normal BMI (18.5–24.9) for a given height.","do_not_use_when":"The person is under 20 years old (children need age- and sex-specific BMI percentiles), or you need body-fat percentage (use body-fat) or calorie needs (use bmr / tdee).","inputs":[{"name":"weight_kg","label":"Weight","type":"number","unit":"kg","required":true,"max":700,"exclusive_min":0,"description":"Body weight in kilograms.","example":70},{"name":"height_cm","label":"Height","type":"number","unit":"cm","required":true,"min":50,"max":300,"description":"Standing height in centimetres.","example":175}],"outputs":[{"name":"bmi","label":"BMI","type":"number","unit":"kg/m²","decimals":2,"description":"Body mass index = weight / height²."},{"name":"category","label":"Category","type":"string","decimals":4,"description":"WHO adult BMI classification."},{"name":"healthy_weight_min_kg","label":"Healthy weight (min)","type":"number","unit":"kg","decimals":1,"description":"Weight at BMI 18.5 for this height."},{"name":"healthy_weight_max_kg","label":"Healthy weight (max)","type":"number","unit":"kg","decimals":1,"description":"Weight at BMI 24.9 for this height."},{"name":"prime","label":"BMI prime","type":"number","decimals":3,"description":"BMI divided by the upper normal limit 25; values above 1 indicate excess weight."}],"input_schema":{"type":"object","properties":{"weight_kg":{"description":"Body weight in kilograms. Unit: kg.","type":"number","maximum":700,"exclusiveMinimum":0,"examples":[70],"x-unit":"kg"},"height_cm":{"description":"Standing height in centimetres. Unit: cm.","type":"number","minimum":50,"maximum":300,"examples":[175],"x-unit":"cm"}},"additionalProperties":false,"required":["weight_kg","height_cm"]},"output_schema":{"type":"object","properties":{"bmi":{"description":"Body mass index = weight / height². Unit: kg/m².","type":"number","x-unit":"kg/m²"},"category":{"description":"WHO adult BMI classification.","type":"string"},"healthy_weight_min_kg":{"description":"Weight at BMI 18.5 for this height. Unit: kg.","type":"number","x-unit":"kg"},"healthy_weight_max_kg":{"description":"Weight at BMI 24.9 for this height. Unit: kg.","type":"number","x-unit":"kg"},"prime":{"description":"BMI divided by the upper normal limit 25; values above 1 indicate excess weight.","type":"number"}}},"formula":"BMI = weight_kg / (height_cm / 100)²","method":"BMI is a screening measure, not a diagnosis: it does not distinguish fat from muscle mass and thresholds were derived from European adult populations. WHO categories: <18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, ≥30 obesity (classes I–III at 30, 35, 40).","sources":[{"name":"WHO – A healthy lifestyle: body mass index","url":"https://www.who.int/europe/news-room/fact-sheets/item/a-healthy-lifestyle---who-recommendations","type":"standard","retrieved_at":"2026-09-23"},{"name":"CDC – Adult BMI categories","url":"https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html","type":"standard","retrieved_at":"2026-09-23"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"70 kg, 175 cm","inputs":{"weight_kg":70,"height_cm":175},"expected":{"bmi":22.86,"category":"Normal weight","healthy_weight_min_kg":56.7,"healthy_weight_max_kg":76.3,"prime":0.914},"url":"https://tttkmbb.com/api/v1/calculate/bmi?weight_kg=70&height_cm=175"},{"name":"95 kg, 180 cm","inputs":{"weight_kg":95,"height_cm":180},"expected":{"bmi":29.32,"category":"Overweight (pre-obesity)"},"url":"https://tttkmbb.com/api/v1/calculate/bmi?weight_kg=95&height_cm=180"}],"faq":[{"q":"Is BMI accurate for athletes?","a":"No. Muscular people can have a high BMI without excess fat, because BMI only uses weight and height. Use body-fat percentage for body composition."},{"q":"Which thresholds are used?","a":"WHO adult thresholds (18.5 / 25 / 30 / 35 / 40). Some Asian populations use lower action points (23 and 27.5) recommended by WHO for public-health action."},{"q":"Does this work for children?","a":"No. For ages 2–19 BMI must be interpreted with age- and sex-specific percentiles (CDC/WHO growth charts), which this calculator does not implement."}],"tags":["bmi","body mass index","weight category","obesity","healthy weight"],"related":[{"calculator_id":"bmr","reason":"Estimate resting calorie needs for the same weight and height."},{"calculator_id":"body-fat","reason":"BMI does not measure body composition; the US Navy method estimates body-fat percentage."},{"calculator_id":"ideal-weight","reason":"Compare with ideal-weight formulas (Devine, Robinson, Miller, Hamwi)."}],"links":{"html":"https://tttkmbb.com/health/bmi","markdown":"https://tttkmbb.com/health/bmi.md","json":"https://tttkmbb.com/health/bmi.json","api":"https://tttkmbb.com/api/v1/calculate/bmi","schema":"https://tttkmbb.com/api/v1/calculators/bmi","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-23"},"timestamp":"2026-09-23T23:30:47Z"}