{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"pack-years"},"result":{"entity_type":"calculator","id":"pack-years","calculator_id":"pack-years","canonical_url":"https://tttkmbb.com/medical/pack-years","name":"Pack-Years Calculator","title":"Pack-Years Calculator – Smoking History from Cigarettes per Day and Years Smoked","category":"medical","category_name":"Medical & Clinical","tool_name":"calculate_pack_years","featured_mcp_tool":false,"description":"Converts a smoking history into pack-years (packs per day × years smoked, 20 cigarettes per pack) and notes the USPSTF lung-cancer screening threshold of 20 pack-years.","use_when":"You need a standardised cumulative smoking exposure for risk assessment or screening eligibility.","do_not_use_when":"Exposure is from cigars, pipes, vaping or smokeless tobacco, for which pack-years are not defined.","inputs":[{"name":"cigarettes_per_day","label":"Cigarettes per day","type":"number","required":false,"min":0,"max":200,"description":"Average cigarettes smoked per day. 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Give this or packs_per_day.","type":"number","minimum":0,"maximum":200,"examples":[20]},"packs_per_day":{"description":"Average packs per day (alternative to cigarettes_per_day).","type":"number","minimum":0,"maximum":10,"examples":[1]},"years_smoked":{"description":"Total years of smoking at that rate. Unit: years.","type":"number","minimum":0,"maximum":100,"examples":[30],"x-unit":"years"},"cigarettes_per_pack":{"description":"Pack size; the pack-year definition uses 20.","type":"integer","minimum":10,"maximum":50,"default":20,"examples":[20]}},"additionalProperties":false,"required":["years_smoked"]},"output_schema":{"type":"object","properties":{"pack_years":{"description":"packs_per_day × years_smoked. 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Results are informational only and not a substitute for clinical judgement or medical advice.","sources":[{"name":"NCI Dictionary of Cancer Terms – pack year","url":"https://www.cancer.gov/publications/dictionaries/cancer-terms/def/pack-year","type":"government","retrieved_at":"2026-09-24"},{"name":"USPSTF (2021) Lung Cancer: Screening – recommendation statement","url":"https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/lung-cancer-screening","type":"standard","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":"20 cigarettes/day for 30 years","inputs":{"cigarettes_per_day":20,"years_smoked":30},"expected":{"pack_years":30,"packs_per_day":1,"total_cigarettes":219150},"url":"https://tttkmbb.com/api/v1/calculate/pack-years?cigarettes_per_day=20&years_smoked=30"},{"name":"Half a pack a day for 15 years","inputs":{"packs_per_day":0.5,"years_smoked":15},"expected":{"pack_years":7.5,"cigarettes_per_day":10},"url":"https://tttkmbb.com/api/v1/calculate/pack-years?packs_per_day=0.5&years_smoked=15"}],"faq":[{"q":"How do I handle changing habits?","a":"Compute each period separately (e.g. 10/day for 5 years = 2.5, then 20/day for 10 years = 10) and add them: 12.5 pack-years."},{"q":"Is 20 pack-years a hard cut-off?","a":"USPSTF 2021 recommends annual low-dose CT for adults aged 50–80 with at least 20 pack-years who smoke or quit within 15 years; other programmes use different thresholds."}],"tags":["pack years","smoking history","lung cancer screening","cigarettes per day"],"related":[{"calculator_id":"age","reason":"Age is part of screening eligibility."},{"calculator_id":"vo2-max","reason":"Cardiorespiratory fitness context."}],"links":{"html":"https://tttkmbb.com/medical/pack-years","markdown":"https://tttkmbb.com/medical/pack-years.md","json":"https://tttkmbb.com/medical/pack-years.json","api":"https://tttkmbb.com/api/v1/calculate/pack-years","schema":"https://tttkmbb.com/api/v1/calculators/pack-years","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T01:46:22Z"}