Pack-Years for Smoking 20 Cigarettes a Day for 40 Years
A lifelong pack-a-day habit over 40 years accumulates 40 pack-years, carrying very high risks of lung disease and cancer.
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.
40 pack-years of smoking history is associated with significantly elevated risks of lung cancer, COPD, and cardiovascular disease.
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.