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Free health tool

Smoking pack-years calculator

Calculate a standardised cigarette pack-year history for one period of smoking at a known average daily rate, without adding a disease-risk band or screening decision.

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  • Instant result
  • No account

Calculate your result

Enter the average for this one period, with no more than one decimal place. Use a full stop for decimals on this English page and no unit or thousands separator.

Accepted range: 0 to 500 cigarettes/day

Enter smoking duration for this period, not age or years since quitting. Up to one decimal place is accepted.

Accepted range: 0 to 100 years

Your result will appear here

Nothing is saved or added to the URL.

What this result means

Enter the average cigarettes smoked per day and the years smoked at that rate. The calculator divides the daily count by the standard 20-cigarette pack, multiplies by years and keeps the result separate from disease risk or screening eligibility. [1][3]

What your pack-year result means

Pack-years combine average cigarette-smoking intensity and duration into one standard history number. One pack-year means the same arithmetic as one standard 20-cigarette pack per day for one year. [1][3]

The result is not the number of calendar years smoked. Ten cigarettes per day for 20 years and 20 cigarettes per day for 10 years both produce 10 pack-years, even though the histories are different.

If your smoking amount changed

This first version calculates one period at one average rate. If the daily amount changed materially, it cannot produce a precise lifetime total. Keep the periods and their rates separate rather than guessing one lifetime average or adding the rounded displays.

Write down each period, its average cigarettes per day and its duration for a health professional. Do not use a self-added total from this one-period tool to decide screening eligibility.

What pack-years leave out

Pack-years do not measure inhaled dose. They leave out inhalation depth, cigarette design, changes within a period, second-hand smoke and individual biology. Equal totals are not proof of equal personal effects.

Do not convert cigars, pipes, waterpipe, roll-your-own tobacco mass, cannabis, heated tobacco, vaping or nicotine pouches into cigarette pack-years. This calculator has no validated universal equivalence for those products.

Why there is no screening or risk label

Pack-years can be one part of a clinical history, but screening recommendations also use other details and differ by country and programme. A number alone cannot decide eligibility. [2][3]

If you have symptoms or questions about screening, speak with a qualified local health professional. This arithmetic result does not diagnose cancer, rule out disease or replace a clinical history.

Private calculation and safe sharing

The calculation runs in your browser. Cigarettes per day, years smoked and the result are not placed in the URL, shared link or analytics.

Share this tool sends only the calculator link after a preview. It never shares your entered smoking history or calculated result.

Formula and assumptions

Formula
Pack-years = (average cigarettes per day ÷ 20) × years smoked. [1][3]
Version
Standard cigarette pack-years for one smoking period, smoking-pack-years-neutral-v1
Rounding
Parse both entries as exact decimals with at most one decimal place, calculate without intermediate rounding and round the displayed pack-years once to one decimal place, half up. A positive result below 0.1 is labelled less than 0.1, never zero.
Worked example
Example: 10 cigarettes per day for 20 years gives (10 ÷ 20) × 20 = 10.0 pack-years. Twenty cigarettes per day for 10 years also gives 10.0 pack-years; the matching total does not make the two histories identical. [3]

Who this is for — and when not to use it

Intended use

Neutral arithmetic for an adult current or former cigarette smoker who knows the average cigarettes per day and duration for one smoking period and wants the standardised pack-year number.

Not intended for

Not a disease-risk calculator, screening eligibility checker, diagnosis, safety category, quit-timeline, treatment guide, nicotine-dose calculation or conversion for products other than cigarettes.

Exclusions

  • Lung-cancer screening eligibility or any country-specific threshold decision
  • Symptoms, diagnosis, disease probability, prognosis, treatment or emergency advice
  • Cigars, pipes, waterpipe, bidis, roll-your-own tobacco mass, cannabis, heated tobacco, vaping, pouches and other nicotine products
  • Second-hand smoke or occupational exposure
  • A smoking history with materially changing intensity represented as one precise lifetime total; this one-period version cannot calculate that total
  • Inferring cigarettes per day from pack price, pack count or purchase history
  • Children and adolescents or anyone using the result as evidence that an exposure level is safe

Evidence sources

  1. 1. Definition of pack year — National Cancer Institute. Accessed Aug 21, 2026.
  2. 2. Lung Cancer: Screening — U.S. Preventive Services Task Force. Accessed Aug 21, 2026.
  3. 3. How the National Lung Cancer Screening Program works — Australian Government Department of Health, Disability and Ageing. Accessed Aug 21, 2026.