About the Pack Year Calculator
Pack Year Calculator works out your pack-years, the number doctors use to describe how much a person has smoked. One pack-year means smoking one pack of 20 cigarettes a day for one year. Enter the cigarettes you smoke or smoked per day and the number of years, and the page gives your pack-years. If you add your age and say whether you still smoke, it also shows whether you meet the US guideline for yearly low-dose CT lung cancer screening: age 50 to 80, at least 20 pack-years, and smoking now or quitting within the last 15 years.
Updated October 2026
How to use the Pack Year Calculator
- 1Enter the number of cigarettes you smoke or smoked per day.
- 2Enter the years you smoked.
- 3Enter your age and whether you still smoke.
- 4If you quit, enter the years since you stopped.
- 5Read your pack-years and the screening note.
What pack-years measure
Pack-years combine how much you smoke and how long you have smoked into one number. It is simple, and doctors use it for health records and decisions about screening. It does not capture everything, because how deeply you inhale, which cigarettes you smoke and how much you were exposed to second-hand smoke also matter.
Examples
Some quick examples show the arithmetic.
- 1 pack a day for 25 years = 25 pack-years
- 10 cigarettes a day for 40 years = 20 pack-years
- 2 packs a day for 10 years = 20 pack-years
- 5 cigarettes a day for 6 years = 1.5 pack-years
Talking to your doctor
If your pack-years are high, ask about screening, lung function tests and help to quit. Support such as nicotine replacement, medicines and counselling roughly doubles the chance of quitting. Quitting is the most effective thing you can do for your lungs at any age.
Related tools
Check your weight with the BMI Calculator and your heart rate zones with the Target Heart Rate Calculator. The Max Heart Rate Calculator and the Calories Burned Calculator can help you plan exercise.
Features
- Pack-years from cigarettes per day and years
- US screening guideline check
- Handles ex-smokers
- Packs per day shown
- Clear, careful wording
- Private: nothing is uploaded
Frequently asked questions
What is a pack-year?
The amount of smoking equal to one pack (20 cigarettes) a day for one year. Smoking two packs a day for 10 years is 20 pack-years.
How do I calculate pack-years?
Divide the cigarettes smoked per day by 20 and multiply by the number of years. 10 cigarettes a day for 20 years is 0.5 × 20 = 10 pack-years.
Why do doctors ask for pack-years?
It estimates your exposure to tobacco smoke and so your risk of lung disease and cancer, and it helps decide who should be screened.
Who should have lung cancer screening in the US?
The US Preventive Services Task Force (2021) recommends yearly low-dose CT for people aged 50 to 80 with at least 20 pack-years who smoke now or quit within the past 15 years. Other countries have different rules.
What if I smoked pipes, cigars or vapes?
Pack-years count only cigarettes. Other tobacco and vaping carry risks that this number does not measure. Tell your doctor about all of them.
Does the risk fall when I quit?
Yes. The risk of heart disease and cancer falls over the years after quitting, and quitting at any age helps.
Is this a diagnosis?
No. It is information only. See a doctor if you have a lasting cough, coughing up blood, breathlessness or unexplained weight loss.
Is a high number always bad?
Risk generally rises with pack-years, but it is not a score for a single person. Two people with the same number can have different health, genes and exposures, so use the figure as a talking point with your doctor.
Does the guideline apply outside the US?
The 20 pack-year rule is the US one. The UK, Canada, Australia and other countries have their own screening programmes with different ages and rules, so ask your local health service.
Is my information kept?
No. It is calculated in your browser and not sent anywhere.