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Smoking Pack Years Calculator

Work out smoking pack years instantly with clear inputs, formula shown and shareable results.

About Smoking Pack Years Calculator

Multiplies packs smoked per day by the number of years smoked, the standard measure of cumulative tobacco exposure.

Formula

Pack years

Pack years = (cigarettes per day / 20) x years smoked

Worked example

With the default values below, Smoking Pack Years Calculator returns Pack years of 15.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Cigarettes per dayaccepts 1–100
20
Years smokedaccepts 0.1–80
15

Results

Pack years
15.00
Packs per day
1.00
Cigarettes smoked in total
109,500

Step by step

  1. 1Values used
  2. 2Pack years
  3. 3Pack years= 15.00
  4. 4Packs per day= 1.00
  5. 5Cigarettes smoked in total= 109,500

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Why 20 cigarettes to a pack?

It is the conventional pack size used to define the unit, regardless of local pack sizes.

What threshold matters for screening?

20 pack years is the current USPSTF threshold for annual low-dose CT lung cancer screening.

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