Work out smoking pack years instantly with clear inputs, formula shown and shareable results.
Multiplies packs smoked per day by the number of years smoked, the standard measure of cumulative tobacco exposure.
Pack years
Pack years = (cigarettes per day / 20) x years smoked
Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
It is the conventional pack size used to define the unit, regardless of local pack sizes.
20 pack years is the current USPSTF threshold for annual low-dose CT lung cancer screening.