How to calculate the smoking pack years?

To calculate the pack-year (PY), multiply the number of packs of cigarettes smoked each day (Packs) by the number of years (Years) smoked by the individual.

  • PY = Packs * Years;


  • PY = (Cigarettes per day/Pack size) * Years, if your pack size differs from the standard 20 cigarettes

If you want to know how many packs (PL) or cigarettes (CL) you’ve smoked in your life, use the following formula:

  • PL = Cigarettes per day * 365.24 * Years
  • CL = (Cigarettes per day/Pack-size) * 365.24 * Years

Take a look other related calculators, such as:

Example of pack-year calculation

One pack-year is the same as smoking 20 cigarettes every day for a year (1 pack * 1 year). If you smoke ten cigarettes per day for two years (0.5 pack * two years). Even two cigarettes per day for ten years (0.1 pack * ten years), you still get one smoking pack-year.

However, it is still controversial if pack years are enough for predicting the risk of lung cancer. Some studies contend that longer durations of smoking (e.g., 40 years at a half pack per day) represent a greater danger than shorter periods (10 years at two packs per day). Even though the number of pack-years is the same in both circumstances.

Health Effects

Tobacco use causes sickness and incapacity, and injury to practically every organ in the body.
More than 16 million Americans suffer from a smoking-related illness. For every person who dies due to smoking, at least 30 others suffer from a significant smoking-related illness. Tobacco smoking is linked to cancer, heart disease, stroke, lung disease, diabetes, and risk for chronic obstructive pulmonary disease (COPD), including emphysema and chronic bronchitis. Smoking also raises the risk of TB, some eye illnesses, and immune system issues such as rheumatoid arthritis.

Secondhand smoke causes around 41,000 fatalities among nonsmokers and 400 deaths among babies each year. In addition, secondhand smoking causes stroke, lung cancer, and coronary heart disease in adults.
Secondhand smoking exposes children to an increased risk of sudden infant death syndrome, acute respiratory infections, middle ear disorders, more severe asthma, respiratory complaints, and slower lung expansion.

Some of the chemicals found in tobacco smoke include:

Tobacco smoke contains thousands of compounds, including at least 70 recognized carcinogens. These cancer causing substances are known as carcinogens. Tobacco smoke contains the following chemicals:

  • Nicotine (the addictive drug that produces the effects in the brain that people are looking for)
  • Hydrogen cyanide
  • Formaldehyde
  • Lead
  • Arsenic
  • Ammonia
  • Radioactive elements, such as polonium-210
  • Benzene
  • Carbon monoxide
  • Tobacco-specific nitrosamines (TSNAs)
  • Polycyclic aromatic hydrocarbons (PAHs)

Many of these compounds are carcinogenic. Some can also cause heart disease, lung illness, and other major health issues.

Frequently Asked Questions

What is a 30 pack-year history?

For example, a person who has smoked 20 cigarettes a day for 30 years has a (20/20) x 30 = 30 pack-year smoking history.

What is 20 pack-year smoker?

For example, a person who has smoked 20 cigarettes a day for 20 years has a (20/20) x 20 = 30 pack-year smoking history.

What is 5 pack-year smoking history?

Haris smoked 10 cigarettes per day for 10 years: 1/2 pack (10 cigarettes) per day x 10 years = 5 pack-years

How do you calculate pack years?

One pack-year is the same as smoking 20 cigarettes every day for a year (1 pack * 1 year).