A typical adult lung is about 9 inches (24 centimeters) tall during normal breathing and stretches to roughly 10.5 inches (27 cm) when fully expanded. Together, both lungs can hold about 6 liters of air, which is roughly the volume of three large soda bottles. But raw dimensions only tell part of the story. Your lungs are surprisingly complex on the inside, with an internal surface area roughly the size of half a tennis court.
Outer Dimensions and Weight
Each lung sits inside your rib cage, extending from just above your collarbone down to your diaphragm. That 9-to-10.5-inch height is the vertical measurement, but width and depth vary quite a bit depending on body size. Despite filling most of your chest cavity, lungs are remarkably light. A healthy lung weighs around 234 grams on average, or just over half a pound. The pair together weighs a little more than a pound, roughly the same as holding two baseballs.
Why Your Two Lungs Aren’t the Same Size
Your right and left lungs are noticeably different. The right lung is shorter and wider, with three separate sections called lobes. It sits a bit higher because your liver pushes up from below. The left lung is longer and narrower, with only two lobes. It also has a curved indentation along its inner surface called the cardiac notch, a scoop-shaped space that makes room for your heart. Because of this, the left lung holds less air than the right. If you’ve ever wondered why your heart seems slightly off-center in your chest, the left lung literally gave up real estate to accommodate it.
How Much Air They Actually Hold
Total lung capacity for a healthy adult is about 6 liters, but you never use all of it during a normal breath. A regular, relaxed breath moves only about 500 milliliters of air in and out, roughly one cup. That means each quiet breath uses less than 10% of what your lungs can hold. The rest stays in reserve for when you need it: during exercise, while climbing stairs, or in any situation that demands faster oxygen delivery.
Even after you exhale as forcefully as possible, about 1.2 liters of air remains trapped in your lungs. This residual air keeps the tiny air sacs from collapsing completely between breaths.
The Hidden Surface Area Inside
The most striking thing about lung size isn’t what you see from the outside. Inside each lung, airways branch repeatedly into smaller and smaller tubes, eventually ending in roughly 480 million tiny air sacs called alveoli. These sacs are where oxygen passes into your blood and carbon dioxide passes out. Spread flat, all those alveoli create a total surface area of about 75 square meters. That’s comparable to the floor space of a one-bedroom apartment, all packed into an organ that fits inside your ribcage. This massive surface area is what makes your lungs so efficient at gas exchange, even when you’re breathing at rest.
What Determines Your Lung Size
Height is the single biggest predictor of lung size. Taller people have larger rib cages and longer torsos, which gives the lungs more room to grow. Sex also plays a role: men typically have larger lung volumes than women of the same height, partly due to differences in chest wall structure and hormonal influences on growth.
Age matters too, but the timeline differs between sexes. In adolescent males, lung and chest development continues during puberty and doesn’t finish until puberty ends. In adolescent females, lung development is mostly complete shortly after the onset of menstruation. After reaching peak capacity, lung function gradually declines with age as the tissues lose elasticity and the chest wall stiffens.
How Altitude Shapes Lung Function
People who grow up at high elevations develop measurably better lung function than those living near sea level. A study comparing 1,000 people from different altitudes found that healthy high-altitude residents scored about 8% higher on measures of how much air they could forcefully exhale compared to their low-altitude counterparts. This isn’t necessarily because their lungs are physically larger, but because the lungs adapt to extract oxygen more efficiently from thinner air. The chest cavity may expand slightly, and the lung tissue itself becomes better at moving air. These adaptations are most pronounced in people who spent their childhood at elevation, suggesting the lungs respond to environmental demands during their growth phase.