Use case · Screening cutoffs · Educational · Updated October 2, 2026
How many pack-years do you need for lung cancer screening?
Direct answer
In the United States the pack-year cutoff is 20. That is one pack a day for 20 years, or half a pack a day for 40 years. USPSTF (ages 50–80) and Medicare (ages 50–77) also require that you smoke now or quit within 15 years. The American Cancer Society uses 20 pack-years at ages 50–80 and does not apply that quit limit.
Guideline cutoffs
| Guideline | Age | Pack-years | After quitting |
|---|---|---|---|
| USPSTF | 50–80 | 20+ | Currently smoke or quit within the past 15 years |
| ACS | 50–80 | 20+ | Current or former smokers — years since quitting does not matter |
| Medicare | 50–77 | 20+ | Currently smoke or quit within the past 15 years |
| Germany | 50–75 | 15+ (and 25+ years smoking) | Currently smoke or quit less than 10 years ago |
| NHS England | 55–74 | No pack-year cutoff | Anyone who has ever smoked |
Germany also requires at least 25 years of smoking. NHS England uses a risk score after the lung health check, not a pack-year minimum.
Two histories, same calculator
| Person | USPSTF | ACS | Medicare |
|---|---|---|---|
| Age 60, smokes now, 30 pack-years | Meets | Meets | Meets |
| Age 66, 30 pack-years, quit 20 years ago | Does not meet | Meets | Does not meet |
“Meets” means the published age, pack-year, and quit rules match. A clinician still decides whether a scan is appropriate. Medicare also requires a shared decision-making visit before the first low-dose CT.
Limits
- U.S. thresholds count cigarette pack-years. Cigar, pipe, and vaping totals are not a substitute.
- Being under 20 pack-years does not mean lung cancer is impossible. Being over 20 does not mean you have it.
- Pack-years stay the same after you quit. Ask a clinician about screening, and call 1-800-QUIT-NOW for quit support.
Use the calculator
The formula: how do you calculate pack-years? Check a history in the pack-year calculator.