Introduction
A pack year is a simple way to measure how much you have smoked over your life. One pack year means you smoked one pack (20 cigarettes) a day for one year.1 Doctors use this number to check your risk for lung cancer.1
This Pack Year Calculator turns your smoking history into that number. Enter how much you smoked each day, the age you started, and the age you stopped. You can add more than one time period, because most people do not smoke the same amount their whole life. If you still smoke, just tick the box and the tool uses your current age.
The calculator also counts other tobacco products, not just cigarettes. You can add cigars, bidis, cigarillos, pipe bowls and loose tobacco. Each one is changed into "cigarette equivalents" so everything adds up into one total.
Your result shows your total pack years, a step-by-step solution, and charts that show where the number comes from. The tool also tells you if you reach 20 pack years, a level often used in lung cancer screening guidelines for people ages 50 to 80 who smoke now or quit in the last 15 years.1
This is an estimate to help you understand your smoking history. Talk to your doctor about screening and next steps.
How to use our Pack Year Calculator
Tell us your age and how much tobacco you smoked at each stage of your life. The calculator shows your total pack years and whether you reach the 20 pack year mark used for lung cancer screening.
Your current age: Type how old you are now in years. This age is used as the stop age for any period where you still smoke.
Amount per product: For each product you used, enter how much you smoked. Cigarettes, cigars, bidis, cigarillos and pipe bowls are counted per day. Loose tobacco is counted per week. Leave a product at zero if you never used it.
Loose tobacco unit: Pick oz or g from the drop-down to match the amount you typed.
Age started: Enter how old you were when you began smoking that product at that amount.
Age stopped: Enter how old you were when you stopped. This must be higher than your start age.
I am still smoking: Tick this box if you have not quit. Your current age is then used as the stop age.
Nonsmoking years: Enter the number of years inside that period when you did not smoke at all. For example, type 2 if you quit for two years and then went back. Leave it at 0 if you smoked the whole time.
Add Another Period: Click this to add a new line when your habit changed. For example, add one period for 5 a day in your twenties and another for 20 a day in your thirties. You can add up to 10 periods per product.
Calculate: Click Calculate to see your pack years, the step-by-step math, the chart by product, and your pack years by age. Click Reset to start over.
What Is a Pack Year?
A pack year is a way to measure how much tobacco a person has smoked over their life. One pack year means smoking one pack of cigarettes (20 cigarettes) every day for one year.1 It mixes two things into one number: how much you smoked each day, and how many years you smoked.
The Pack Year Formula
The math is simple:
Pack years = (cigarettes per day ÷ 20) × years smoked1
So a person who smoked 20 cigarettes a day for 30 years has 30 pack years. A person who smoked 10 a day for 30 years has 15 pack years. Someone who smoked 40 a day for 15 years also has 30 pack years.
Why Doctors Use Pack Years
Lung damage adds up. The more years a person smokes and the more cigarettes they smoke each day, the higher the risk of lung cancer.2 The longer people smoke, the higher the risk of COPD (chronic bronchitis and emphysema).6 Smoking also causes heart disease and stroke. Pack years give doctors one clear number to judge that risk instead of guessing.
Pack years are used most often for lung cancer screening. In the United States, guidelines suggest a yearly low-dose CT scan for adults aged 50 to 80 who have 20 or more pack years and who still smoke or quit within the last 15 years.1 Lung cancer found early is much easier to treat.
Other Tobacco Products
Cigarettes are not the only way people smoke. Cigars, pipes and bidis also burn tobacco and hurt your lungs. To count them, each one is changed into "cigarette equivalents".10 These are common estimates:
| Product | Cigarette equivalents |
|---|---|
| 1 cigarette | 1 |
| 1 bidi (beedi) | 19 |
| 1 cigarillo or small cigar | 1.510 |
| 1 pipe bowl | 2.510 |
| 1 medium cigar | 210 |
| 1 large cigar | 410 |
| 12.5 g loose tobacco | 2011 |
| 1 oz (28.35 g) loose tobacco | 45 |
These are rough guides, not exact rules. Whether a person inhales also changes the risk.
Water pipe (hookah) smoking is not converted. During a typical waterpipe session the smoker draws doses of toxicants ranging from less than one to tens of cigarette equivalents, depending on the toxicant.5 No single number fits all of them.
Breaks and Quit Periods
Many people quit for a while and then start again. Those quit years do not count toward your total. If you smoked from age 20 to 40 but stopped for 3 years in the middle, you count 17 smoking years, not 20.
What Your Number Means
The more pack years, the more smoke your lungs have taken in. The U.S. Preventive Services Task Force recommends a yearly low-dose CT scan for lung cancer for adults aged 50 to 80 with a 20 pack year history who smoke now or quit within the past 15 years.1 Screening stops once a person has not smoked for 15 years or has a health problem that limits life expectancy or the ability to have lung surgery.1
Good News About Quitting
Your pack year total never goes down, because it counts what you have already smoked. But quitting still helps a lot. Risk of heart attack drops sharply within 1 to 2 years.3 Lung cancer risk keeps falling the longer you stay smoke free.3 It is never too late to stop.
Important Note
Pack years are an estimate based on memory, so the number is a guide, not a lab result. It does not include secondhand smoke, vaping, or chewing tobacco. Talk to a doctor about your own risk and whether screening is right for you.