Smoking history quantification for lung cancer and COPD risk assessment.
Pack-years is a measure of smoking history used to assess risk for smoking-related diseases. One pack-year equals smoking one pack (20 cigarettes) per day for one year.
Formula: (Cigarettes per day ÷ 20) × Years smoked = Pack-years
Example: A person who smoked 10 cigarettes per day for 40 years would have 20 pack-years (0.5 × 40 = 20)
Low risk
Moderate risk
High risk
Very high risk