Pack-Years: How to Calculate Them, Screening Eligibility, and the Cost of Smoking
October 29, 2026
Pack-years is a measure of cumulative smoking exposure used by clinicians to assess risk. The formula is packs smoked per day × number of years smoked. A pack contains 20 cigarettes. Someone who smoked 1.5 packs (30 cigarettes) a day for 20 years has 30 pack-years. Someone who smoked 10 cigarettes a day for 30 years has 0.5 × 30 = 15 pack-years.
The measure ties together intensity and duration, but it does not capture everything, such as the age of starting or the time since quitting.
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In the United States, lung cancer screening with low-dose CT is recommended by the US Preventive Services Task Force for adults aged 50 to 80 who have a smoking history of at least 20 pack-years and currently smoke or quit within the past 15 years. Criteria are updated periodically, and insurers may have their own rules, so confirm current guidelines with your clinician. If you have quit, the risk falls over time but remains elevated for years compared with never-smokers.
| Pattern | Calculation | Pack-years |
|---|---|---|
| 1 pack/day for 20 years | 1 x 20 | 20 |
| 1.5 packs/day for 20 years | 1.5 x 20 | 30 |
| 10 cigarettes/day for 30 years | 0.5 x 30 | 15 |
| 2 packs/day for 15 years | 2 x 15 | 30 |
| 5 cigarettes/day for 40 years | 0.25 x 40 | 10 |
The Financial Cost
At $9 a pack, one pack a day costs $9 × 365 = $3,285 a year, or $273.75 a month. Over 30 years at an unchanged price, that is $98,550. If instead the same $3,285 were invested each year at an average 5% return, it would grow to 3,285 × ((1.05³⁰ − 1) ÷ 0.05) = 3,285 × 66.44 = about $218,000. The calculation excludes higher health and life insurance premiums, health costs, and lost productivity. Prices and taxes vary by state and country, so use your local price.
Benefits of Quitting
Within 20 minutes heart rate and blood pressure drop; within a year, the excess risk of coronary heart disease falls to about half that of a continuing smoker; within 5 to 15 years, stroke risk can approach that of nonsmokers; and lung cancer risk continues to decline over a decade or more. Quitting at any age brings benefits. Combination approaches (counseling plus medication or nicotine replacement) increase success rates. Quitlines (1-800-QUIT-NOW in the US) offer free support.
Using the Numbers
Calculate your pack-years and discuss screening with your healthcare provider if you are in the eligible age range. Use the cost calculation as motivation, and allocate the saved money to a goal such as an emergency fund or a vacation. This article is general information, not medical advice.
Frequently Asked Questions
How are pack-years calculated?
Packs per day multiplied by years smoked.
How many cigarettes are in a pack?
20.
Who is eligible for lung cancer screening in the US?
Adults 50 to 80 with at least 20 pack-years who currently smoke or quit within 15 years.
How much does a pack a day cost per year at $9?
$3,285.
Does quitting help at any age?
Yes.