Table 1 Pack-years of smoking

To calculate smoking pack-years:

  Divide the number of cigarettes smoked per day by 20 (the number of cigarettes in a pack)

  Then multiply by the number of years smoked

ex. 1

(70 cigarettes/day ÷ 20 cigarettes/pack) × 10 years = 35 pack-years

ex. 2

(35 cigarettes/day ÷ 20 cigarettes/pack) × 20 years = 35 pack-years

ex. 3

(20 cigarettes/day ÷ 20 cigarettes/pack) × 20 years = 20 pack-years