Pack-years calculator
Enter how much you smoked per day, in packs or cigarettes, and for how many years, to see the pack-years that history adds up to. The number clinicians use to describe smoking history, and it runs entirely in your browser.
Medically reviewed by Kevin Brandstetter, M.D.Updated September 28, 2026
Your average over the years you smoked. A pack is 20 cigarettes.
One smoking period. Decimals are fine, such as 2.5 for two and a half years.
Your pack-years
Enter how much and how long
Pack-years appear here once the amount per day and the years smoked are filled in.
A calculation, not a diagnosis.
Pack-years are arithmetic on a smoking history: how much, for how long. The number does not measure lung health, and it does not decide whether a screening test is right for you. This tool is for adults. A licensed clinician reads a smoking history alongside everything else in your record.
Methodology
- How this is calculated
- Pack-years are packs smoked per day multiplied by years smoked. A cigarette count is divided by 20 first, because a pack is 20 cigarettes. One pack-year is the same as smoking an average of one pack, 20 cigarettes, every day for a year. The result is shown to one decimal. The tool counts one smoking period at one average rate.
- Where the data comes from
- US Preventive Services Task Force, Lung Cancer: Screening, final recommendation statement (March 9, 2021; JAMA 2021;325(10):962–969, doi:10.1001/jama.2021.1117), which defines one pack-year as an average of 20 cigarettes, one pack, per day for a year.
- Last updated
- September 28, 2026
- What this does not account for
- Changes in how much you smoked over time, breaks, other tobacco or nicotine products, secondhand smoke, and every other fact a clinician weighs. Someone who smoked at different rates in different periods can add the pack-years of each period. The tool takes no age or quit date, so it makes no screening decision.
Where pack-years come up
Lung cancer screening guidance is one place. In its 2021 recommendation, the US Preventive Services Task Force recommends a low-dose CT scan every year for adults aged 50 to 80 who have a smoking history of 20 pack-years or more and who currently smoke or quit within the past 15 years. It graded that recommendation B. It says screening should stop once a person has not smoked for 15 years, or develops a health problem that substantially limits life expectancy or the ability or willingness to have curative lung surgery.
That is information about a published recommendation, not a decision about you. Whether screening fits your situation is a conversation with a clinician, and the Task Force describes it as a shared decision about benefits, limitations, and harms.
Nothing here is stored
Your answers stay in your browser. They are not sent to Temi, not saved, not attached to you, and not recorded in any session replay, and closing the tab clears them. Temi knows only that someone opened this tool, the same thing it knows about every page.
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