Pack-Year Smoking Calculator

Cumulative cigarette smoking exposure in pack-years.

For educational and clinical reference. Not a substitute for medical judgment. See the medical disclaimer.
Pack-years
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Interpretation
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References

  1. US Preventive Services Task Force. Screening for Lung Cancer: Recommendation Statement. JAMA. 2021;325(10):962-970.

How to use

  1. Enter average cigarettes per day and total years smoked.
  2. Pack-years = (cigarettes/day × years) ÷ 20.
  3. Use the result to assess lung cancer screening eligibility (≥ 20 py per USPSTF).

Frequently asked questions

What is a pack-year?

One pack (20 cigarettes) per day for one year = 1 pack-year. Pack-years quantify cumulative cigarette smoke exposure.

Why does pack-year history matter?

It correlates with risk of lung cancer, COPD, and cardiovascular disease and is a primary criterion for lung cancer screening eligibility.

What thresholds qualify for lung cancer screening?

USPSTF (2021) recommends annual low-dose CT screening for adults age 50–80 with a ≥ 20 pack-year history who currently smoke or quit within the past 15 years.

How do I count for someone who quit?

Multiply average cigarettes per day during the smoking period by the years smoked, then divide by 20. Pack-years do not decline after quitting — they reflect lifetime exposure.

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