Turn cigarettes per day and years smoked into pack-years, the standard lifetime smoking exposure measure.
Result
How to use this tool
Use the average over the smoking period.
Count total years, including breaks if they were short.
This is the standard lifetime exposure measure.
The advanced section records years since quitting.
Formula & worked example
20 cigarettes per day for 30 years is 1 pack per day x 30 years = 30 pack-years.
Limitations — read this before you rely on it
Exposure arithmetic only, using 20 cigarettes per pack. It does not estimate any individual cancer risk. This tool is for education only and is not medical advice. Talk to a clinician about any result that worries you, and never change treatment because of a calculator result.
Frequently asked questions
One pack of 20 cigarettes per day for one year. Half a pack for 40 years is also 20 pack-years.
It summarises lifetime dose and is used in lung cancer risk and screening eligibility discussions.
No. Pack-years stay as a history measure, though risk falls with time since quitting.
Pack-years are defined for cigarettes. Other products need separate risk assessment.
Many programmes use around 20 pack-years with age criteria, but rules vary by country.