Pack year

Pack year, abbreviated py, is way to quantify the amount a person has smoked.

Definition

NCI defines it as:

${\text{1 py}}={\frac {\text{1 pack}}{day}}\times {\text{1 year}}$

Note:

• A standard pack has 20 cigarettes.

Examples

Example 1

1 pack per day for 40 years: 40 py.

Example 2

2 packs per day for 10 years: 20 py.

Example 3

3 cigarettes per day for 50 years: 3/20 * 50 = 7.5 py.

Example 4

Half a pack per day for 20 years: 10 py.

See also

• Smoking.