Follow the calculation
Pack-years = (average cigarettes per day ÷ 20) × years smoked. The result is shown to one decimal place. Exposure bands and the 20 pack-year threshold use the unrounded value so that rounding cannot incorrectly move a result over the boundary.
| Daily average | Years | Calculation | Pack-years |
|---|---|---|---|
| 10 | 10 | (10 ÷ 20) × 10 | 5 |
| 20 | 10 | (20 ÷ 20) × 10 | 10 |
| 40 | 10 | (40 ÷ 20) × 10 | 20 |
If your history has several periods
Break your history into periods with a similar daily average. Work out the pack-years for each period and add them. Time without cigarettes adds no cigarette pack-years. If the averages are uncertain, tell your clinician that they are estimates rather than presenting the final number as exact.
Why the threshold is not an eligibility decision
The US USPSTF recommendation considers a combination of age, cigarette exposure and quit history. It also requires an individual discussion about screening benefits, harms and suitability for treatment. This tool does not collect enough information to make that decision, and a US recommendation is not a guarantee of eligibility or service availability in Pakistan.
Prepare for a clinical discussion in Pakistan
Bring a timeline of cigarette use and any quit dates. Mention other tobacco products separately; this formula cannot convert them into cigarettes. Ask a qualified healthcare professional about appropriate assessment and support to stop. Confirm services, appointments and costs directly with the provider; this page does not publish an unverified local quit-line number.
Frequently asked questions
What does one pack-year mean?
It is the exposure from averaging 20 cigarettes each day for one year. Multiply packs per day by years smoked. For example, 10 cigarettes daily for 20 years is 10 pack-years.
What if my smoking changed over time?
Work out each period separately and add the results. Ten cigarettes a day for 10 years contributes 5 pack-years; 20 a day for another 5 years contributes 5 more. Entering a single daily average is only an approximation.
Does this calculator decide screening eligibility?
No. It calculates cigarette exposure. The US USPSTF recommendation also considers age 50–80, current smoking or quitting within the past 15 years, and suitability for treatment. A clinician must discuss benefits and harms; local practice can differ.
Do my pack-years fall after I quit?
Past exposure remains part of your history. Stopping smoking stops additional cigarette exposure from accumulating. Tell your clinician when you stopped; that information matters independently of the pack-year total.
Is a low or zero pack-year result reassuring?
This number cannot rule out illness or establish safety. It counts the cigarette history entered and does not measure symptoms, second-hand smoke, other exposures, or individual cancer risk. WHO states that no level of tobacco exposure is safe.
Can shisha, naswar or gutka be converted?
This cigarette-based formula does not provide a reliable conversion for those products. Tell your clinician separately about all forms of tobacco use. Do not assume an uncounted product is harmless.
Are the exposure bands official risk categories?
No. The bands below 10, 10 to below 20, 20 to below 40, and 40 or more are descriptive groups used by this interface. They do not predict a cancer probability or establish a safe exposure level.
How is the PKR cost estimate calculated?
It uses average cigarettes per day × years × 365 × the rate you enter. This assumes the same daily consumption and price for the whole period, so it is an illustration rather than a record of actual past spending.