What a pack-year is
A pack-year measures lifetime exposure to cigarette smoke: one pack (20 cigarettes) a day for one year. Smoking 10 cigarettes a day for 20 years gives 10 pack-years, and so does two packs a day for 5 years. Doctors use it because the risk of lung cancer, COPD and heart disease rises with the total amount smoked, not just the number of years.
Pack-years = cigarettes per day ÷ 20 × years of smoking
Worked example: 15 cigarettes a day for 20 years
- 15 ÷ 20 = 0.75 pack a day.
- 0.75 × 20 years = 15 pack-years.
- That is 15 × 365.25 × 20 = 109,575 cigarettes.
- At $9 a pack, the habit costs about $2,465 a year ($205 a month) and has cost about $49,309 at today’s price.
- Quitting now would keep about $24,654 in your pocket over the next ten years.
Pack-years by daily consumption (20 years)
| Cigarettes a day | Pack-years | Cost per year at $9 |
|---|---|---|
| 5 | 5 | $822 |
| 10 | 10 | $1,644 |
| 15 | 15 | $2,465 |
| 20 | 20 | $3,287 |
| 30 | 30 | $4,931 |
| 40 | 40 | $6,575 |
Lung cancer screening
The US Preventive Services Task Force recommends a yearly low-dose CT scan for adults aged 50 to 80 who have a smoking history of 20 pack-years or more and who currently smoke or quit within the past 15 years. Screening finds cancers earlier, when they are easier to treat. Most private insurance plans and Medicare cover it; ask your doctor whether it applies to you.
Other forms of tobacco
The pack-year was designed for cigarettes. For roll-your-own tobacco, a rough equivalence is one cigarette per 0.5 to 1 gram of tobacco. Cigars and pipes carry their own risks, but there is no standard conversion; tell your doctor what and how much you smoke.
What quitting changes
- Within a year, the excess risk of heart disease falls by about half.
- After 10 to 15 years, the risk of lung cancer is roughly halved compared with continuing to smoke.
- Pack-years never go back down, but your risk does, which is why screening rules include people who quit recently.
Free help is available: call 1-800-QUIT-NOW or visit smokefree.gov. Nicotine replacement or prescription medication roughly doubles the chance of quitting, and adding counseling raises it further.