Pack-Year Calculator

Calculate smoking pack-years from cigarettes per day and years smoked, and check the USPSTF lung cancer screening criteria.

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Enter your values. The result updates as you type; press Calculate to confirm and jump to the result on mobile. Use Share to send the calculator with your result.

Pack-year formula

pack-years = (cigarettes per day ÷ 20) × years smoked

One pack-year is smoking 20 cigarettes (one pack) a day for a year. Example: 30 cigarettes a day for 20 years = 1.5 × 20 = 30 pack-years. If your smoking changed over time, add the pack-years from each period.

Lung cancer screening

The USPSTF (2021) recommends a yearly low-dose CT scan for adults aged 50 to 80 with at least a 20 pack-year history who currently smoke or quit within the past 15 years. Medicare and most insurers cover it for eligible people.

Why it matters

Doctors use pack-years to estimate risk of lung cancer and COPD. Risk rises with total exposure, but there’s no safe level, and it starts falling soon after quitting.

Frequently asked questions

How many pack-years is a pack a day for 10 years?

10 pack-years.

Do cigars or vapes count?

The pack-year measure is for cigarettes; tell your doctor about other tobacco or nicotine use separately.

About this tool

Written by
[Author: to be assigned]
Reviewed by
Expert review pending
Last updated
31 Oct 2026

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