Pack-Years Calculator
Find smoking pack-years from packs and years.
1 pack = 20 cigarettes
Results update as you type.
This calculator provides estimates based on population research. Results are not medical advice. Consult a qualified healthcare provider before making health or nutrition decisions.
How it works
Pack-years are a standard way clinicians quantify a person's lifetime cigarette exposure, and this calculator computes the figure from smoking intensity and duration. You enter the average number of packs smoked per day and the number of years smoked, and it returns the total pack-years. The measure multiplies the two: one pack per day for one year is one pack-year, and the number scales with both how much and how long someone smoked. Since a standard pack holds twenty cigarettes, half a pack a day is ten cigarettes; enter it as 0.5. Pack-years matter because they correlate with the risk of smoking-related diseases, especially lung cancer and chronic obstructive pulmonary disease, and they are used in medical guidelines to decide who should be screened. For example, lung cancer screening recommendations often use a threshold such as twenty pack-years of history in a certain age range. Calculating your pack-years gives a concrete summary of exposure that is more informative than years smoked alone, since two people who smoked for the same time may have very different intensities. This is an educational tool, not medical advice; screening decisions and health risk depend on many factors and should be discussed with a healthcare provider. Enter your packs per day and years smoked to compute your pack-years.
Pack-years = packs per day × years smoked
Pack-years multiply the average number of packs of cigarettes smoked per day by the number of years a person has smoked. One pack contains twenty cigarettes. Smoking one pack a day for one year equals one pack-year; two packs a day for ten years equals twenty pack-years. It standardizes lifetime tobacco exposure into a single number.
Source:National Cancer Institute
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter packs per day and years smoked.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Pack-years updates instantly as you type — no button to press.
Frequently asked questions
What is a pack-year?
A pack-year is a unit that quantifies lifetime cigarette exposure. One pack-year equals smoking one pack, or twenty cigarettes, per day for one year. It combines how much and how long a person smoked into a single number, which clinicians use to assess smoking-related health risks and screening eligibility.
How do you calculate pack-years?
Multiply the average number of packs smoked per day by the number of years smoked. Someone who smoked one and a half packs a day for twenty years has thirty pack-years. Since a pack is twenty cigarettes, enter fractional packs for smaller amounts, such as 0.5 for ten cigarettes a day. The calculator does the multiplication.
Why do pack-years matter?
Pack-years correlate with the risk of smoking-related diseases, particularly lung cancer and chronic obstructive pulmonary disease. Higher pack-years mean greater cumulative exposure and higher risk. Medical guidelines use pack-year thresholds, often around twenty or more, along with age, to determine who should undergo lung cancer screening, making the number clinically useful.
How do I count if my smoking varied over time?
If your daily amount changed, calculate pack-years for each period separately using the packs per day and years for that period, then add them together. For example, one pack a day for ten years plus two packs a day for five years is ten plus ten, or twenty pack-years total.
Is this medical advice?
No. This calculator provides an educational estimate of your smoking exposure. It does not assess your personal disease risk or determine screening eligibility, which depend on many factors including age, family history, and current smoking status. Discuss your pack-years and health with a qualified healthcare provider for guidance on screening and risk.