Pack-Year Calculator

Pack-years are a simple way to measure how much someone has smoked over their lifetime. Enter your average daily amount and how many years you smoked, and this calculator does the math for you.

How do you want to enter how much you smoked?

One pack = 20 cigarettes.

Leave out years when you had fully stopped.

Not medical advice

This tool gives general information only. It can’t diagnose any condition or tell you whether you need a test or treatment. Talk to a doctor about your own health. If you have severe breathlessness, chest pain, are coughing up blood or your lips look blue, call 911 (US) or 999 (UK). See our Medical Disclaimer.

How it works

One pack-year means smoking an average of 20 cigarettes (one pack) a day for one year. The formula is:

Pack-years = (cigarettes per day ÷ 20) × years smoked

So 10 cigarettes a day for 20 years is 10 pack-years, and 1 pack a day for 20 years is 20 pack-years. The result is rounded to one decimal place.

What pack-years can and can’t tell you

  • Pack-years describe how much tobacco smoke you have been exposed to. They are not a diagnosis and can’t tell you whether you have a lung condition.
  • The measure was built for cigarettes. Cigars, pipes, rolling tobacco and vapes don’t convert neatly into pack-years, so this tool doesn’t try to.
  • If your smoking changed a lot over time, work out each period separately and add them together for a better estimate.

Why pack-years matter for screening

In the US, the Preventive Services Task Force recommends yearly lung cancer screening with a low-dose CT scan for adults aged 50 to 80 who have a smoking history of at least 20 pack-years and who smoke now or quit within the past 15 years. Screening should stop once a person has not smoked for 15 years, or if a health problem limits life expectancy or the ability to have lung surgery. The CDC repeats these criteria and advises talking with your doctor about the possible benefits and harms first.

Screening has downsides as well as benefits, including false alarms that lead to more tests, and radiation from repeated scans. That is why the decision is meant to be made together with a clinician.

For readers in the UK, the NHS is rolling out lung cancer screening in England for people aged 55 to 74 who are current or former smokers. It is only available in some areas so far.

Don’t wait for screening if you have symptoms

See a doctor about a cough that lasts more than 3 weeks, coughing up blood, ongoing breathlessness, chest pain or unexplained weight loss. Screening is for people without symptoms.

Frequently asked questions

Divide the number of cigarettes you smoked per day by 20 to get packs per day, then multiply by the number of years you smoked. For example, 15 cigarettes a day for 40 years is (15 ÷ 20) × 40 = 30 pack-years.

It means a smoking history equal to one pack a day for 20 years, or two packs a day for 10 years. In the US, 20 pack-years is one of the criteria used to decide who may be offered yearly lung cancer screening.

No. Pack-years were designed for cigarettes. E-cigarettes deliver nicotine very differently, so there is no accepted way to convert vaping into pack-years. Tell your doctor about any vaping separately.

Only your doctor can confirm that. US guidance from the Preventive Services Task Force covers adults aged 50 to 80 with at least 20 pack-years who smoke now or quit within the past 15 years. Insurance rules can differ, so check with your plan too.

No. The calculation happens in your browser. Nothing you type is sent to us or stored.

Sources

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