Quantify your cumulative smoking exposure.
Pack years = (cigarettes per day / 20) × years smoked. One pack = 20 cigarettes. Example: 1 pack/day × 20 years = 20 pack-years. Pack-years quantify cumulative exposure and correlate with lung cancer risk, COPD, and cardiovascular disease. USPSTF recommends LDCT screening for adults 50–80 with ≥ 20 pack-years.