How old are your lungs?

Lung age is the idea that your lungs can be older than you are. Popularized by the NHS and Australian health agencies, it estimates how much of your lung function has been lost to smoking and expresses it as an age. A forty-year-old who has smoked a pack a day for twenty years might have the lungs of a fifty-five-year-old.

The calculator above uses a simple formula — chronological age plus a fraction of your pack-years — to give you a quick estimate. For a precise number, you would need a spirometry test at a clinic. But the estimate is good enough to make the damage visible, and that is the point: most people who see their real lung age make a different decision the next morning.