how to calculate pack year
The pack-year is a unit for measuring the amount a person has smoked over a long period of time. It is calculated by multiplying the number of packs of cigarettes smoked per day by the number of years the person has smoked. For example, 1 pack-year is equal to smoking 20 cigarettes (1 pack) per day for 1 year, or 40 cigarettes per day for half a year, and so on. One pack-year is the equivalent of 365.24 packs of cigarettes or 7,305 cigarettes. Calculation. Number of pack-years = (packs smoked per day) Ã (years as a smoker) or