{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"heart-rate-zones"},"result":{"entity_type":"calculator","id":"heart-rate-zones","calculator_id":"heart-rate-zones","canonical_url":"https://tttkmbb.com/health/heart-rate-zones","name":"Heart Rate Zone Calculator","title":"Target Heart Rate Zone Calculator – Max HR (Tanaka/Fox) and Karvonen Zones","category":"health","category_name":"Health","tool_name":"calculate_heart_rate_zones","featured_mcp_tool":false,"description":"Estimates maximum heart rate from age (Tanaka or Fox formula) and computes the five training zones, using the Karvonen heart-rate-reserve method when resting heart rate is supplied.","use_when":"You need training heart-rate ranges (zones 1–5) for an adult from age, optionally refined by resting heart rate.","do_not_use_when":"The person takes heart-rate-limiting medication (e.g. beta blockers) or has a measured maximum heart rate from a test (use that instead of an age formula).","inputs":[{"name":"age_years","label":"Age","type":"number","unit":"years","required":true,"min":5,"max":120,"description":"Age in years.","example":30},{"name":"resting_heart_rate","label":"Resting heart rate","type":"number","unit":"bpm","required":false,"min":25,"max":150,"description":"Optional resting heart rate; when given, zones use the Karvonen (heart-rate reserve) method.","example":60},{"name":"max_hr_formula","label":"Max HR formula","type":"enum","required":false,"default":"tanaka","values":[{"value":"tanaka","label":"Tanaka: 208 − 0.7 × age"},{"value":"fox","label":"Fox: 220 − age"}],"description":"Formula for maximum heart rate. Tanaka (2001) is more accurate across ages than the classic 220 − age.","example":"tanaka"}],"outputs":[{"name":"max_heart_rate","label":"Maximum heart rate","type":"number","unit":"bpm","decimals":0,"description":"Estimated maximum heart rate."},{"name":"method","label":"Zone method","type":"string","decimals":4,"description":"'karvonen' when resting HR provided, otherwise 'percent_of_max'."},{"name":"zones","label":"Training zones","type":"list","decimals":0,"description":"Five zones with intensity range, lower and upper bpm and purpose."}],"input_schema":{"type":"object","properties":{"age_years":{"description":"Age in years. Unit: years.","type":"number","minimum":5,"maximum":120,"examples":[30],"x-unit":"years"},"resting_heart_rate":{"description":"Optional resting heart rate; when given, zones use the Karvonen (heart-rate reserve) method. Unit: bpm.","type":"number","minimum":25,"maximum":150,"examples":[60],"x-unit":"bpm"},"max_hr_formula":{"description":"Formula for maximum heart rate. Tanaka (2001) is more accurate across ages than the classic 220 − age.","type":"string","enum":["tanaka","fox"],"default":"tanaka","examples":["tanaka"]}},"additionalProperties":false,"required":["age_years"]},"output_schema":{"type":"object","properties":{"max_heart_rate":{"description":"Estimated maximum heart rate. Unit: bpm.","type":"number","x-unit":"bpm"},"method":{"description":"'karvonen' when resting HR provided, otherwise 'percent_of_max'.","type":"string"},"zones":{"description":"Five zones with intensity range, lower and upper bpm and purpose.","type":"array"}}},"formula":"max_hr = 208 − 0.7·age (Tanaka) or 220 − age (Fox). Percent-of-max: zone = max_hr × %. Karvonen: target = (max_hr − resting) × % + resting. Zones: 50–60, 60–70, 70–80, 80–90, 90–100%.","sources":[{"name":"Tanaka H, Monahan KD, Seals DR (2001) Age-predicted maximal heart rate revisited, J Am Coll Cardiol 37:153-156","url":"https://pubmed.ncbi.nlm.nih.gov/11153730/","type":"peer_reviewed","retrieved_at":"2026-09-23"},{"name":"Karvonen MJ, Kentala E, Mustala O (1957) The effects of training on heart rate, Ann Med Exp Biol Fenn 35:307-315","url":"https://pubmed.ncbi.nlm.nih.gov/13470504/","type":"peer_reviewed","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":"Age 30, Tanaka, no resting HR","inputs":{"age_years":30},"expected":{"max_heart_rate":187,"method":"percent_of_max"},"url":"https://tttkmbb.com/api/v1/calculate/heart-rate-zones?age_years=30"},{"name":"Age 40, resting 60, Fox","inputs":{"age_years":40,"resting_heart_rate":60,"max_hr_formula":"fox"},"expected":{"max_heart_rate":180,"method":"karvonen"},"url":"https://tttkmbb.com/api/v1/calculate/heart-rate-zones?age_years=40&resting_heart_rate=60&max_hr_formula=fox"}],"faq":[{"q":"Why use Karvonen?","a":"It scales zones by heart-rate reserve (max − resting), so fitter people with low resting rates get more realistic targets than a plain percentage of max."},{"q":"How accurate are age formulas?","a":"Individual maximum heart rate varies by about ±10–12 bpm around any age formula. A supervised maximal test gives the real value."}],"tags":["heart rate zones","target heart rate","max heart rate","karvonen","training zones"],"related":[{"calculator_id":"running-pace","reason":"Pair heart-rate zones with pace targets."}],"links":{"html":"https://tttkmbb.com/health/heart-rate-zones","markdown":"https://tttkmbb.com/health/heart-rate-zones.md","json":"https://tttkmbb.com/health/heart-rate-zones.json","api":"https://tttkmbb.com/api/v1/calculate/heart-rate-zones","schema":"https://tttkmbb.com/api/v1/calculators/heart-rate-zones","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-23"},"timestamp":"2026-09-23T23:32:54Z"}