{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"bmr"},"result":{"entity_type":"calculator","id":"bmr","calculator_id":"bmr","canonical_url":"https://tttkmbb.com/health/bmr","name":"BMR Calculator","title":"BMR Calculator – Basal Metabolic Rate (Mifflin-St Jeor and Harris-Benedict)","category":"health","category_name":"Health","tool_name":"calculate_bmr","featured_mcp_tool":true,"description":"Estimates basal metabolic rate (calories burned at complete rest per day) with the Mifflin-St Jeor equation, and also reports the revised Harris-Benedict estimate.","use_when":"You need resting daily calorie needs for an adult from sex, weight, height and age, as a base for diet or TDEE calculations.","do_not_use_when":"You need total daily calories including activity (use tdee), the person is a child, pregnant, or has very high muscle mass (use a body-fat based equation such as Katch-McArdle instead).","inputs":[{"name":"sex","label":"Biological sex","type":"enum","required":true,"values":[{"value":"male","label":"Male","aliases":["m","man"]},{"value":"female","label":"Female","aliases":["f","woman"]}],"description":"Biological sex used to select the formula coefficients.","example":"male"},{"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":"Height in centimetres.","example":175},{"name":"age_years","label":"Age","type":"number","unit":"years","required":true,"min":18,"max":120,"description":"Age in years (adults only).","example":30}],"outputs":[{"name":"bmr_kcal_per_day","label":"BMR (Mifflin-St Jeor)","type":"number","unit":"kcal/day","decimals":0,"description":"Basal metabolic rate by the Mifflin-St Jeor equation (recommended by the Academy of Nutrition and Dietetics)."},{"name":"harris_benedict_kcal_per_day","label":"BMR (Harris-Benedict, revised 1984)","type":"number","unit":"kcal/day","decimals":0,"description":"Basal metabolic rate by the Roza & Shizgal 1984 revision of Harris-Benedict, for comparison."},{"name":"bmr_kj_per_day","label":"BMR (kJ)","type":"number","unit":"kJ/day","decimals":0,"description":"Mifflin-St Jeor BMR expressed in kilojoules (1 kcal = 4.184 kJ)."}],"input_schema":{"type":"object","properties":{"sex":{"description":"Biological sex used to select the formula coefficients.","type":"string","enum":["male","female"],"examples":["male"]},"weight_kg":{"description":"Body weight in kilograms. Unit: kg.","type":"number","maximum":700,"exclusiveMinimum":0,"examples":[70],"x-unit":"kg"},"height_cm":{"description":"Height in centimetres. Unit: cm.","type":"number","minimum":50,"maximum":300,"examples":[175],"x-unit":"cm"},"age_years":{"description":"Age in years (adults only). Unit: years.","type":"number","minimum":18,"maximum":120,"examples":[30],"x-unit":"years"}},"additionalProperties":false,"required":["sex","weight_kg","height_cm","age_years"]},"output_schema":{"type":"object","properties":{"bmr_kcal_per_day":{"description":"Basal metabolic rate by the Mifflin-St Jeor equation (recommended by the Academy of Nutrition and Dietetics). Unit: kcal/day.","type":"number","x-unit":"kcal/day"},"harris_benedict_kcal_per_day":{"description":"Basal metabolic rate by the Roza & Shizgal 1984 revision of Harris-Benedict, for comparison. Unit: kcal/day.","type":"number","x-unit":"kcal/day"},"bmr_kj_per_day":{"description":"Mifflin-St Jeor BMR expressed in kilojoules (1 kcal = 4.184 kJ). Unit: kJ/day.","type":"number","x-unit":"kJ/day"}}},"formula":"Mifflin-St Jeor: BMR = 10·weight_kg + 6.25·height_cm − 5·age_years + 5 (male) or − 161 (female). Harris-Benedict (1984): male 88.362 + 13.397·W + 4.799·H − 5.677·A; female 447.593 + 9.247·W + 3.098·H − 4.330·A.","method":"Mifflin-St Jeor (1990) predicts resting energy expenditure within ±10% for about 82% of non-obese and 70% of obese adults, which is why it is preferred over the older Harris-Benedict equation.","sources":[{"name":"Mifflin MD et al. (1990) A new predictive equation for resting energy expenditure, Am J Clin Nutr 51:241-247","url":"https://pubmed.ncbi.nlm.nih.gov/2305711/","type":"peer_reviewed","retrieved_at":"2026-09-24"},{"name":"Roza & Shizgal (1984) The Harris Benedict equation reevaluated, Am J Clin Nutr 40:168-182","url":"https://pubmed.ncbi.nlm.nih.gov/6741850/","type":"peer_reviewed","retrieved_at":"2026-09-24"}],"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":"Male, 70 kg, 175 cm, 30 years","inputs":{"sex":"male","weight_kg":70,"height_cm":175,"age_years":30},"expected":{"bmr_kcal_per_day":1649,"harris_benedict_kcal_per_day":1696,"bmr_kj_per_day":6898},"url":"https://tttkmbb.com/api/v1/calculate/bmr?sex=male&weight_kg=70&height_cm=175&age_years=30"},{"name":"Female, 60 kg, 165 cm, 40 years","inputs":{"sex":"female","weight_kg":60,"height_cm":165,"age_years":40},"expected":{"bmr_kcal_per_day":1270,"harris_benedict_kcal_per_day":1341},"url":"https://tttkmbb.com/api/v1/calculate/bmr?sex=female&weight_kg=60&height_cm=165&age_years=40"}],"faq":[{"q":"What is the difference between BMR and TDEE?","a":"BMR is energy used at complete rest. TDEE multiplies BMR by an activity factor (1.2–1.9) to estimate total daily energy expenditure; use the tdee calculator for that."},{"q":"Why do the two formulas differ?","a":"They were fitted on different populations (Harris-Benedict in 1919, revised 1984; Mifflin-St Jeor in 1990). Mifflin-St Jeor is generally more accurate for modern adults."}],"tags":["bmr","basal metabolic rate","resting energy expenditure","calories","mifflin st jeor","harris benedict"],"related":[{"calculator_id":"tdee","reason":"Multiply BMR by an activity factor to get total daily calories."},{"calculator_id":"macros","reason":"Split a calorie target into protein, carbohydrate and fat grams."}],"links":{"html":"https://tttkmbb.com/health/bmr","markdown":"https://tttkmbb.com/health/bmr.md","json":"https://tttkmbb.com/health/bmr.json","api":"https://tttkmbb.com/api/v1/calculate/bmr","schema":"https://tttkmbb.com/api/v1/calculators/bmr","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-23T23:33:25Z"}