What this calculator does
Smoking pack-years works out cumulative smoking exposure used in clinical risk screening. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaPack-years = (cigarettes per day / 20) × years smoked
The inputs explained
| Field | What to enter |
|---|---|
| Cigarettes per day | A number. Starts at 20. |
| Years smoked | A number. Starts at 10. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with cigarettes per day
Every other input is held at the calculator’s starting values while cigarettes per day varies. Select any row to load that scenario into the calculator.
How the answer changes with cigarettes per day
| Cigarettes per day | Pack-years | Note |
|---|---|---|
| 10 | 5.0 | 20 pack-years or more is commonly used as a screening threshold for lung cancer imaging: discuss with a clinician. |
| 15 | 7.5 | 20 pack-years or more is commonly used as a screening threshold for lung cancer imaging: discuss with a clinician. |
| 20 | 10.0 | 20 pack-years or more is commonly used as a screening threshold for lung cancer imaging: discuss with a clinician. |
| 30 | 15.0 | 20 pack-years or more is commonly used as a screening threshold for lung cancer imaging: discuss with a clinician. |
| 40 | 20.0 | 20 pack-years or more is commonly used as a screening threshold for lung cancer imaging: discuss with a clinician. |
| 60 | 30.0 | 20 pack-years or more is commonly used as a screening threshold for lung cancer imaging: discuss with a clinician. |