Skip to content
Health Calculators

Pack Years Calculator

Verified formula Updated Jun 2026 Private — runs on your device

Enter details
Verified formula Private

Pack years

10.00

For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.

How to use the Pack Years Calculator

The Pack Years Calculator works out your pack years in an instant. Enter cigarettes per day and years smoked and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.

  1. Enter the cigarettes per day.
  2. Enter the years smoked.
  3. Read off your pack years — the calculator updates automatically, with no button to press.

Formula

The Pack Years Calculator uses the formula:

Pack years = Cigarettes per day ÷ 20 × Years smoked

Worked example

For example, with cigarettes per day of 20 and years smoked of 10, the pack years is 10.00.

Inputs used
Cigarettes per day 20
Years smoked 10
Results
Pack years 10.00

Results are estimates for educational use, not professional advice.

Frequently asked questions

A pack year is smoking 20 cigarettes (one pack) a day for one year. Smoking 20 a day for 10 years is 10 pack years.

Divide cigarettes per day by 20 to get packs, then multiply by the number of years smoked.

It summarises lifetime smoking exposure in one number, which helps assess the risk of lung disease and decide on screening.

No, pack years record past exposure and do not fall. But quitting greatly reduces your future health risk over time.

Enter the cigarettes per day. Enter the years smoked. Read off your pack years — the calculator updates automatically, with no button to press.

Related calculators