Pack-Year Exposure
The pack-year metric quantifies lifetime cigarette exposure. 1 pack-year = smoking 20 cigarettes (1 pack) per day for one year. Enter each period with different smoking patterns to calculate cumulative exposure.
Pack-years
10.0
Screen for lung cancer when ≥20 pack-years (USPSTF)
Total years smoking
10.0
Average packs per day
1.00
Clinical considerations
- ≥20 pack-years + currently smoking or quit within 15 years: eligible for annual low-dose CT screening (age 50–80).
- High pack-years increase risk for COPD, cardiovascular disease, and peripheral vascular disease.
- Use pack-year history to assess surgical risk and need for perioperative lung function testing.
How to Use This Calculator
Break history into consistent periods
Capture changes in smoking intensity over time (e.g., 10 cigs/day for 5 years, 20 cigs/day for 15 years).
Check special situations
For cigar, pipe, or vaping, consult conversion resources to estimate cigarette equivalents.
Discuss screening and cessation
Positive thresholds should trigger conversations about CT screening, pulmonary function tests, and quit planning.
Formula
Pack-years = (Cigarettes per day ÷ 20) × Years smoked
Total pack-years = Σ pack-years for all smoking periods
Average packs/day = (Σ (cigarettes/day × years) ÷ total years) ÷ 20
Full Description
Pack-year history is a cornerstone of lung cancer screening eligibility and respiratory risk assessment. Collecting accurate exposure data helps identify patients for low-dose CT scans, smoking cessation programmes, and COPD management. Combine pack-year calculations with carbon monoxide testing, spirometry, and cardiovascular screening to guide holistic care.
Frequently Asked Questions
What if the person quit years ago?
Include all past smoking years. Pack-years stay in medical history even after quitting; they guide screening eligibility.
How do I factor reduced smoking?
Record separate periods for different intensities (e.g., 30 cigs/day for 10 years, 10 cigs/day for 5 years).
Does vaping count?
No official conversion yet. Document vaping separately and assess nicotine dependence using tools like HSI or FTND.
What about cigars or pipe tobacco?
Use clinical judgement—estimate cigarette equivalents or consult guidelines. Many screening programmes still rely on pack-year (cigarette-based) history.