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Calculation Machine

Pack Year Calculator

Smoking history in pack years.

Reviewed by James Whitfield · How we check our maths

Your values

ⓘ Live results

Results
Pack years
16.5
Total cigarettes
120,450
Screening eligible (US 20+)
Not by pack years alone
Packs consumed
6,023

Quick answer

One pack year equals smoking 20 cigarettes a day for a year; 20+ pack years usually triggers screening eligibility.

The formula

Pack years = (Cigarettes/day ÷ 20) × Years

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Cigarettes per day15
  • Years smoked22

Result

  • Pack years16.5
  • Total cigarettes120,450
  • Screening eligible (US 20+)Not by pack years alone
  • Packs consumed6,023

How to use the Pack Year Calculator

  1. 1Enter your average cigarettes per day.
  2. 2Enter total years smoked.
  3. 3Compare with the 20 pack year screening threshold.

Frequently asked questions

What if my habit varied?

Average across periods, or add pack years for each period separately.

Does quitting reset it?

No, pack years are cumulative, but risk does fall after quitting.

About this calculator