eGFR Calculator
Kidney filtration estimate.
Open →
Health
Pack-Year Calculator
Find your smoking pack-years from cigarettes per day and years smoked.
Pack-years
—
Smoking history.
| Packs per day | — |
|---|---|
| Years | — |
| — | |
| — |
Show our math
Enter your figures above to see the step-by-step working.
Educational estimate — not medical adviceEverything computed client-side — nothing leaves this page
How the Pack-Year Calculator Works
A pack-year measures lifetime cigarette exposure. One pack-year equals smoking one pack (20 cigarettes) a day for one year. Divide cigarettes per day by 20 to get packs per day, then multiply by the number of years smoked. Someone who smoked a pack a day for 15 years has 15 pack-years.
Pack-years help gauge risk and guide screening — for example, lung-cancer screening is often recommended for adults with a 20-pack-year history. If your habit changed over time, add up each period separately.
pack-years = (cigarettes per day ÷ 20) × years smoked
Frequently Asked Questions
How do you calculate pack-years?
Divide cigarettes smoked per day by 20 (a pack), then multiply by the number of years smoked. A pack a day for 20 years is 20 pack-years.
Why do pack-years matter?
They estimate cumulative smoking exposure, which correlates with lung-cancer and COPD risk and is used to decide who should be screened.
What if my smoking varied over the years?
Add up each period separately — calculate the pack-years for each stretch at its rate and sum them.
More From The Desk
Same plain method, different figuresMean Arterial Pressure Calculator
Average arterial pressure.
Open →Corrected Sodium Calculator
Sodium corrected for glucose.
Open →A1C
Same plain method, different figures.
Open →Body Surface Area
Same plain method, different figures.
Open →