Pack-Years for 20 Cigarettes a Day for 20 Years

Smoking 20 cigarettes a day for 20 years equals 20 pack-years.

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How to use this tool

Enter cigarettes per day and years smoked in the fields above.
Results update instantly as you type — or click Calculate.
Read your pack-years and the full breakdown beneath it.

Calculate the pack-year score for a classic one-pack-a-day habit sustained over 20 years.

Frequently asked questions

What is a pack-year?: One pack-year equals smoking one pack (20 cigarettes) every day for one year. Smoking half a pack for 20 years also equals 10 pack-years.
Why do pack-years matter?: Guidelines recommend annual low-dose CT lung cancer screening for adults aged 50–80 with 20+ pack-years of smoking history. Pack-years are also used to gauge COPD and cardiovascular disease risk.