Smoking Pack-Year Calculator

Work out each period on its own and add them up. For example, 20 a day for 5 years is 5 pack-years, and 10 a day for the next 10 years is another 5, so 10 pack-years in total. The calculator takes one period at a time. Counting the years after a relapse matters too; an overall average tends to underestimate the real exposure.

Pack-years are defined for cigarettes, so cigars and pipes don't convert cleanly. A doctor can judge that exposure separately when deciding about screening.

E-cigarettes don't fit the pack-year measure, because nicotine intake varies with the device, the liquid and how it's used. The lung-screening criteria from USPSTF and the American Cancer Society are written in cigarette pack-years.

The US Preventive Services Task Force (2021) recommends a yearly low-dose CT scan for adults aged 50 to 80 with at least a 20 pack-year history who smoke now or quit within the last 15 years. The American Cancer Society uses the same age range and pack-years for people who smoke or used to smoke, without the 15-year limit. This calculator checks the pack-year part only; the decision is made with a doctor and coverage depends on the insurer.

No — pack-years are cumulative lifetime exposure. They don't reset or decrease when you quit. The risk does fall after quitting: the CDC says the added risk of lung cancer drops by half 10 to 15 years after stopping. Time since quitting is a separate figure, and USPSTF uses it in its criteria.