Smoking pack-years calculator
This tool turns a smoking history into one standard number, useful for a doctor visit or lung screening eligibility.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter cigarettes per day and years smoked.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Pack-years = (cigarettes per day ÷ 20) × years smoked, since a standard pack holds 20 cigarettes.
Example
Inputs: Cigarettes per day = 20, Years smoked = 10 years. Result: Pack-years: 10; Packs per day: 1.
Limits and caveats
- It assumes a steady amount; if it changed, calculate each period on its own and add them up.
- It does not cover shisha, cigars or e-cigarettes.
Questions about this tool
What is one pack-year?
Smoking one pack of 20 cigarettes a day for a year. Ten cigarettes a day for twenty years is 10 pack-years.
Why do doctors ask about it?
It helps estimate the risk of diseases such as lung cancer and COPD, and decides eligibility for early screening.
What is the lung cancer screening threshold?
Since 2021 the USPSTF recommends yearly low-dose CT for adults aged 50 to 80 with 20 pack-years or more who smoke now or quit within 15 years.