Each pack represents 1 actual packs
Pack-years is a measure of cigarette smoking calculated by multiplying the number of packs smoked per day by the number of years smoked. Medical professionals use this metric to assess lung cancer risk and determine screening eligibility. Even if you've quit smoking, your pack-year history remains important for health assessments.
Multiply the number of packs smoked per day by the number of years you have smoked. For example, if you smoke 10 cigarettes a day (0.5 packs) for 20 years, the calculation is 0.5 × 20 = 10 pack-years.
It means the cumulative exposure equals smoking one pack (20 cigarettes) daily for 30 years, or two packs daily for 15 years, or any combination where packs × years = 30.
One pack-year is the equivalent of smoking one standard pack (20 cigarettes) every day for one full year.
It is shorthand for 20 pack-years: the total exposure reached by smoking one pack daily for 20 years, two packs daily for 10 years, etc. In the U.S., 20 pack-years plus age 50-80 is a key criterion for lung-cancer screening.
Definition, formula, and clinical significance.
Step-by-step guide with 3 worked examples.
Risk chart by exposure level, COPD, smoking index.
The USPSTF screening threshold explained.
Risk and screening for heavy smokers.
Risk levels for lighter smoking histories.