Quit Smoking and Nicotine Math
Pack-year calculator.
A pack-year is one pack (20 cigarettes) a day for one year. Enter how much you smoked and for how long. If your habit changed, use up to three periods. Optionally add your age and the years since you quit to see the US screening criteria next to your number. Runs in your browser; nothing is sent or stored.
Not medical advice. This tool does arithmetic on the numbers you enter. Talk to a doctor, pharmacist or quit coach before you change how you quit. In the US you can call 1-800-QUIT-NOW (1-800-784-8669); in Canada call 1-866-366-3667 toll-free to talk to a quit coach.
Your smoking history
Your pack-years
Fill the form and press Calculate.
Worked example
Smoking 20 cigarettes a day for 25 years is 1 pack a day for 25 years, which is 25.0 pack-years. If your habit changed, add the periods: 10 cigarettes a day for 8 years (4.0 pack-years) plus 20 a day for 12 years (12.0) is 16.0 pack-years. A person at 30 cigarettes a day (1.5 packs) for 20 years has 30.0. Entering age 58 and 3 years since quitting for the first case shows all three screening criteria met.
How it works
pack-years = (cigarettes per day / 20) x years smoked, added across periods. The USPSTF defines it the same way: one pack-year is the equivalent of smoking an average of 20 cigarettes, 1 pack, per day for a year. The screening check compares your entries with the USPSTF recommendation text: adults aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years. It is a US recommendation shown as information; it is not a diagnosis, an invitation or a statement about what your own province, state or insurer covers.
Sources and basis (opened 2026-10-08): Lung Cancer: Screening (Recommendation), United States Preventive Services Taskforce. Quitline numbers: Speak to a Quit Smoking Counselor, Smokefree.gov (1-800-QUIT-NOW) and Quitting smoking: Provincial and territorial services, Health Canada (Canada.ca) (1-866-366-3667), both opened 2026-10-08.
Not medical advice. This tool does arithmetic on the numbers you enter. Talk to a doctor, pharmacist or quit coach before you change how you quit. In the US you can call 1-800-QUIT-NOW (1-800-784-8669); in Canada call 1-866-366-3667 toll-free to talk to a quit coach.
FAQ
How do you calculate pack-years?
Divide cigarettes smoked per day by 20 to get packs per day, then multiply by years smoked. 20 cigarettes a day for 25 years is 25.0 pack-years.
What is 20 pack-years?
It is the equivalent of 1 pack (20 cigarettes) a day for 20 years, or 2 packs a day for 10 years, or half a pack a day for 40 years. The USPSTF lung cancer screening recommendation uses a 20 pack-year smoking history as one of its criteria.
Does this tell me if I should be screened?
No. It shows your pack-years next to the USPSTF criteria so you can raise the question. Whether screening is right for you is a decision with a clinician, and rules differ by country and insurer.
What if I smoked cigars, a pipe or vaped?
Pack-years is defined in cigarettes. This tool does not convert other products, so it leaves them out rather than guess.
What if I smoked a different amount in different years?
Use the three periods. Each one is cigarettes per day divided by 20, times its years, and the periods are added.