Pack Year Calculator

To calculate the pack year (PY), multiply the number of packs of cigarettes smoked per day (Packs) by the number of years (Years) the person has smoked.

• PY = Packs × Years

or

• PY = (Cigarettes per day/Pack size) × Years, if your pack size is different than the standard 20 cigarettes.

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

• PL = (Cigarettes per day/Pack_size) × 365.24 × Years
• CL = Cigarettes per day × 365.24 × Years

One pack year is equivalent to smoking 20 cigarettes a day for one year (1 pack × 1 year). If you are smoking ten cigarettes daily for two years (0.5 pack × 2 years), or two cigarettes per day in your ten years smoking history (0.1 pack × 10 years), it still gives us one smoking pack year.

However, it is still debatable if pack years are good enough for assessing the risk of lung cancer. Some researchers claim that more prolonged exposure to smoke (e.g., 40 years, a half pack per day) poses a higher risk than shorter periods (10 years with two packs per day) even though the number of pack years is the same in both cases.

In the pack and smoking details section of the pack year calculator, you can change the pack size if your packs differ from the standard ones. Also, you can display the packs and cigarettes smoked in a lifetime - these values usually speak more to our imagination than abstract smoking pack years.