Pack years calculator

Negative daily counts or negative durations are rejected with invalid_input so form mistakes never invent a lifetime dose.

How to call the API and what comes back

Send a JSON body with two required finite non-negative numbers: cigarettes_per_day (aliases cpd, cigarettes, cigs_per_day, cigs, daily_cigarettes) and years_smoked (aliases years, years_of_smoking, smoking_years, duration_years). Absolute values must stay within the published limits of two hundred cigarettes per day and one hundred twenty years so intermediate products remain finite in IEEE double precision on the Worker and in the browser. On success the response echoes rounded cigarettes_per_day and years_smoked, sets packs_per_day to daily cigarettes divided by twenty, pack_years to the product of packs per day and years, cigarettes_per_pack to the constant twenty, formula to the pack-year expression string, message to a short English summary, and steps to an ordered array of substitution lines. Failed validation—missing fields, non-finite numbers, negative cigarettes or years, or values outside absolute limits—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item and zero marginal unit price.

Practical tips, limits, and related searches

Keep daily cigarette counts and durations inside the published absolute range so the product cannot overflow into a non-finite pack-year total that the solver must reject. Prefer sending numbers rather than pre-formatted strings when you control the client; string numbers are accepted only when they match a strict finite numeric pattern. Prefer this capability when you already have average cigarettes per day and years smoked and only need the pack-year product; if your source is a word problem, extract those two numbers first and convert packs-per-day narratives into cigarettes by multiplying by twenty. When teaching, pair examples: twenty cigarettes daily for ten years yields ten pack-years; forty cigarettes daily for five years also yields ten; half a pack (ten cigarettes) for four years yields two; deliberate negative cigarettes or negative years demonstrates the hard invalid_input path; and zero cigarettes with any years (or zero years with any cigarettes) demonstrates the zero pack-year success path for never-smokers. This landing targets people searching for a pack years calculator, smoking pack-year total, or cigarettes per day times years smoked online; it is not a lung-cancer risk model, not a cotinine converter, and not a tool for pipe, cigar, or e-cigarette pack-equivalents. Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately send negative years. Round-trip checks are easy: recompute cigarettes divided by twenty times years by hand and confirm it equals the published pack_years within the same twelve-decimal rounding, and confirm that flipping only the sign of an input flips the response from success to invalid_input.