Addiction Nicotine Use What Is a Pack-Year and How Does It Relate to Me? A Measure of Lifetime Exposure to Tobacco Toxins By Terry Martin Terry Martin Facebook Twitter Terry Martin quit smoking after 26 years and is now an advocate for those seeking freedom from nicotine addiction. Learn about our editorial process Updated on October 22, 2021 Medically reviewed Verywell Mind articles are reviewed by board-certified physicians and mental healthcare professionals. Medical Reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Armeen Poor, MD Medically reviewed by Armeen Poor, MD Armeen Poor, MD, is a board-certified pulmonologist and intensivist. He specializes in pulmonary health, critical care, and sleep medicine. Learn about our Medical Review Board Print Knaupe / E+ / Getty Images Table of Contents View All Table of Contents Examples Loose Tobacco Why Pack-Years Matter Other Ways to Assess Risk As of Dec. 20, 2019, the new legal age limit is 21 years old for purchasing cigarettes, cigars, or any other tobacco products in the U.S. "Pack-year" is a term used to describe the approximate number of cigarettes a person has smoked over time. One pack-year equals 20 manufactured cigarettes smoked per day for one year. Examples of Pack-Years Here are a few examples of how pack-years are determined. For the purposes of the calculation, one pack contains 20 cigarettes. John smoked 10 cigarettes per day for 10 years: 1/2 pack (10 cigarettes) per day x 10 years = 5 pack-yearsJane smoked 30 cigarettes per day for 26 years: 1 pack (20 cigarettes) per day x 26 years = 26 pack-years. Plus 10 cigarettes (1/2 pack) per day x 26 years = 13 pack-years. 26 pack-years + 13 pack-years = 39 pack-yearsChris smoked 40 cigarettes per day for 42 years: 2 packs (40 cigarettes) x 42 years = 84 pack-years What About Loose Tobacco? The pack-year calculation uses standard manufactured cigarettes. But what if you use loose tobacco to roll your own cigarettes or fill a pipe? The pack-year formula can't be applied to people who smoke using loose tobacco. Instead, a translation can be derived by measuring the weight of tobacco in traditional cigarettes and relating it to loose tobacco. Approximately 1/2 ounce of loose tobacco equals 20 commercial cigarettes. Even though there are some differences between the cigarettes you roll yourself with loose tobacco and manufactured cigarettes you buy in a pack, the American Cancer Society reminds consumers that there are health consequences to any type of cigarette you smoke. Here's the formula to gauge pack-years for loose tobacco smokers, who usually quantify how much they smoke in terms of ounces per week: Ounces per week × 2/7 × number of years smoked = pack-years. Why Pack-Years Matter So why is knowing a person's pack-year calculation helpful? Here we take a look at how pack-years could be useful and the debate surrounding the accuracy of how the calculation is used. Assess Lung Cancer Risk Pack-years is one measure of lung cancer risk for people who smoke. According to the Centers for Disease Control and Prevention (CDC), a person's pack-years, age, and smoking history are used to determine whether screening for lung cancer is recommended. However, there is some debate about the accuracy and usefulness of using pack-years as a risk assessment for lung cancer. For example, you might assume that a person who has smoked half a pack of cigarettes every day for 40 years (20 pack-years) is at greater risk for lung cancer than someone who has been smoking two packs a day for 10 years (also 20 pack-years). The assertion assumes that less smoking-related health damage occurs within the first 10 years a person smokes compared to the level of damage sustained after 40 years. However, research has shown that even occasional smoking has health consequences. While it's not a perfect measure of risk, many researchers and clinicians feel that pack-years provide an important perspective on lifetime risk for people who smoke. Assess Risk of Other Smoking-Related Diseases In addition to lung cancer, a person's pack-year calculation is one of several factors considered when assessing a person's risk of smoking-related cardiovascular disease and chronic obstructive pulmonary disease (COPD). However, studies have suggested that other factors such as smoking duration or intensity, rather than just pack-years, may be important to consider when it comes to risk for heart disease and COPD. While measuring pack-years is comparative in nature, it's important to note that the calculation shouldn't be used to justify a smoking habit (e.g., "My smoking isn't that bad" or "At least I don't smoke as much as other people"). Even someone who smokes less or whose pack-year calculation is smaller than another person's can experience serious health issues related to smoking. Other Ways to Assess Risk Pack-years are a reasonable measure of the overall exposure smokers and former smokers have had to the toxins in cigarettes in their lifetime, but it isn't the only predictor of smoking-related disease. While smoking is the top risk factor for lung cancer, there are other things that can contribute as well. For example, according to the American Cancer Society, exposure to radon, asbestos—and other toxic chemicals found in some workplaces, air pollution, and secondhand smoke as well as a family history of lung cancer can all be risk factors. Older age is also a risk factor when it comes to lung cancer. If you want to calculate your risk for lung cancer, the American Association for Thoracic Surgery (AATS) provides a tool for people ages 55 to 79 that takes several risk factors into account; the calculator can even assess your lung cancer risk if you have never smoked. The National Cancer Institute also has an online tool that assesses risk of lung cancer for adults 50 to 80 years old. Smoking Cessation Help Smoking cessation is a scary thought for many smokers, but it's never too late to quit. Start by learning about developing strong quit muscles, the supplies to have on hand when you quit, and nicotine withdrawal. Was this page helpful? Thanks for your feedback! So you're ready to finally quit smoking? Our free guide can help you get on the right track. Sign up and get yours today. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit 14 Sources Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. National Cancer Institute (NCI). Definition of pack year. NCI Dictionary of Cancer Terms. Wood DM, Mould MG, Ong SB, Baker EH. "Pack year" smoking histories: What about patients who use loose tobacco?. Tob Control. 2005;14(2):141-2. doi:10.1136/tc.2004.009977 The American Cancer Society. Is Any Type of Smoking Safe?. Janjigian YY, McDonnell K, Kris MG, et al. Pack-years of cigarette smoking as a prognostic factor in patients with stage IIIB/IV nonsmall cell lung cancer. Cancer. 2010;116(3):670–675. doi:10.1002/cncr.24813 Centers for Disease Control and Prevention (CDC). Who should be screened for lung cancer?. CDC Division of Cancer Prevention and Control. Peto J. That the effects of smoking should be measured in pack-years: Misconceptions 4. Br J Cancer. 2012;107(3):406–407. doi:10.1038/bjc.2012.97 Schane RE, Ling PM, Glantz SA. Health effects of light and intermittent smoking: A review. Circulation. 2010;121(13):1518–1522. doi:10.1161/CIRCULATIONAHA.109.904235 Lubin J, Caporaso N. Misunderstandings in the misconception on the use of pack-years in analysis of smoking. Br J Cancer. 2013;108:1218–1220. doi:10.1038/bjc.2013.76 Lubin JH, Couper D, Lutsey PL, Woodward M, Yatsuya H, Huxley RR. Risk of cardiovascular disease from cumulative cigarette use and the impact of smoking intensity. Epidemiology. 2016;27(3):395-404. doi:10.1097/EDE.0000000000000437 Bhatt SP, Kim Y, Harrington KF, et al. Smoking duration alone provides stronger risk estimates of chronic obstructive pulmonary disease than pack-years. Thorax. 2018;73(5):414-421. doi:10.1136/thoraxjnl-2017-210722 Inoue-Choi M, Liao LM, Reyes-Guzman C, Hartge P, Caporaso N, Freedman ND. Association of long-term, low-intensity smoking with all-cause and cause-specific mortality in the National Institutes of Health–AARP diet and health study. JAMA Intern Med. 2017;177(1):87-95. doi:10.1001/jamainternmed.2016.7511 American Cancer Society. Lung cancer risk factors. US Preventive Services Task Force, Krist AH, Davidson KW, et al. Screening for lung cancer: US preventive services task force recommendation statement. JAMA. 2021;325(10):962-970. doi:10.1001/jama.2021.1117 Jaklitsch MT, Jacobson FL. Lung Cancer Risk Assessment Tool. American Association for Thoracic Surgery (AATS). Additional Reading Arenberg D. "Quick, Where Is My Cigarette?": Mining Tobacco History for More Information on Risk. J Thorac Oncol. 2017;12(11):1606-1607. doi:10.1016/j.jtho.2017.09.090 Lubin JH, Caporaso NE. Cigarette smoking and lung cancer: Modeling total exposure and intensity. Cancer Epidemiol Biomarkers Prev. 2006;15(3):517-23. doi:10.1158/1055-9965.EPI-05-0863 Rothman KJ, Greeland S. Modern Epidemiology. Third. (Lash T, Greenland S, Rothman K, eds.). Philadelphia: Lippincott Williams & Wilkins; 2008:103. Get Treatment for Addiction Advertiser Disclosure × The offers that appear in this table are from partnerships from which Verywell Mind receives compensation.