Long-time smokers are often asked how much they smoke and for how long they’ve been smoking. It’s essential for medical professionals to know how many cigarettes their patients are smoking to get a better idea of their overall health. The nicotine in cigarettes could also affect treatments and medication options. As a way to measure the amount an individual has smoked over a long period of time, a “pack year” is a helpful way to understand this cumulative volume.

How To Calculate a Pack Year

According to the National Cancer Institute at the National Institutes of Health (NIH)¹, a pack year is calculated by multiplying the number of packs of cigarettes smoked per day by the number of years an individual has smoked. They also share the example of smoking 1 pack per day for 1 year is equal to 1 pack year. Likewise, if a person smokes 10 cigarettes per day (½ of a pack) for 10 years, that equals 5 pack years (½ pack x 10 years). The higher the pack year number, the more likely a smoker is to have health issues.

It’s important to note that this pack year formula only applies to manufactured cigarettes. If you roll your own cigarettes with loose tobacco, the math will be slightly different. However, the risks of smoking either commercial cigarettes or loose tobacco cigarettes are comparable and can lead to significant health issues.

Why Does a Pack Year Matter?

At a glance, pack years can tell your doctor your risk level for developing lung cancer and lung disease as a result of smoking cigarettes. Using this number, it’s clear to see that a light smoker who has been smoking for 40 years has just as much risk as a heavy smoker who has been smoking for half that time. It takes into account how much you smoke and how long you’ve been smoking to identify who is most at risk for lung cancer and other health issues.

Pack Years and Lung Cancer Screenings

Along with a person’s age and smoking history, pack years are another way to determine whether an individual should be screened for lung cancer. Lung cancer screenings can detect abnormalities in the lungs that are more easily treated when caught early.

The U.S. Preventive Services Task Force (USPSTF)² recommends an annual lung cancer screening using a low-dose CT lung scan for all adults from the ages of 50 to 80 who have a 20 pack-year smoking history. This applies to all current smokers or anybody who quit smoking within the past 15 years. With lung cancer being the leading cause of cancer deaths in the United States², it’s more important than ever to assess a person’s risk for developing lung cancer and to try and catch it as early as possible for successful treatment.

Pack Years and Heart Disease

Unfortunately, the risk of smoking cigarettes doesn’t stop at lung-related health issues. Nicotine and other chemicals found in cigarettes can have a negative impact on other parts of the body, including the heart and cardiovascular system. According to a study published in the Journal of Invasive Cardiology³, smokers with more than 40 pack years had about 4 times more risk for peripheral artery disease with increased risks for coronary heart disease and stroke than non-smokers.

Peripheral artery disease is characterized by a buildup of cholesterol in the arteries that carry blood to the legs, resulting in reduced blood flow, pain in the limbs, diminished wound-healing abilities in the legs and several other symptoms that can become serious. The study found a direct connection between peripheral artery disease and a higher number of pack years.

Pack Years and Smoker Classification

Smokers can also be classified using pack years to describe their smoking habits to healthcare providers. BMC Public Health⁴ shares these classifications as:

  • 0 Pack Years – Never Smokers
  • 1 – 20 Pack Years – Light Smokers
  • 1 – 40 Pack Years – Moderate Smokers
  • More than 40 Pack Years – Heavy Smokers

How smokers are classified can affect the treatment methods and approaches doctors will choose when individuals are dealing with health problems. It is also a common question on health history forms to get a better idea of a person’s risk for developing future problems.

Proactive Lung Disease Screenings

For heavy smokers with more than 40 pack years, you have the highest risk of developing lung cancer, lung disease, heart disease and other major health issues. It’s never easy to quit smoking, especially if you’ve been a smoker for a long time and it has become part of your routine. However, it’s not too late! No matter how long or how much you’ve been smoking, the health benefits of quitting are almost immediate and will continue to get better the longer you’re able to curb the habit.

If you’re ready to take control of your health, the Preventative Diagnostic Center in Las Vegas is ready to help with accessible low-dose CT scans. Knowing the status of your health now is such an essential step to improving your overall well-being. Using the results from your CT scan, you’ll understand exactly what to work on and how aggressively you should make life changes to achieve your health goals. Contact our team today to learn about our lung CT scans, heart CT scans and other body scans that will help you stay on top of your health and work towards a long active life with your loved ones.


¹ National Cancer Institute at the National Institutes of Health (NIH). NCI Dictionaries: Pack Year. Retrieved 4 May 2021.

² U.S. Preventative Services Task Force (USPSTF). (9 March 2021). Lung Cancer: Screening. Retrieved 4 May 2021.

³ Journal of Invasive Cardiology. (25 July 2019). Study Quantifies Smoking’s Strong Link to Peripheral Artery Disease. Retrieved 4 May 2021.

⁴ Lee, Young-Hoon, Shin, Min-Ho et. al. (11 February 2011). Cumulative smoking exposure, duration of smoking cessation, and peripheral arterial disease in middle-aged and older Korean men. Retrieved 4 May 2021.

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