Your skin is the largest organ. The biggest solid internal organs are your liver, brain, lungs, heart, and kidneys. The medical community is also exploring whether the network of fluid-filled spaces supported by a mesh of connective tissue may also be considered an organ.

An organ is a group of tissues that has a unique purpose. They perform vital life-supporting functions, like pumping blood or eliminating toxins.

Many resources state that there are 79 known organs in the human body. Together, these structures keep us alive and make us who we are.

But according to recent research, there may be even more organs in the body. This includes the interstitium, a structure that some experts think is the new biggest organ.

To date, the skin is considered to be the largest organ. It covers your whole body and makes up about 16 percent of your overall body mass. Your skin is approximately 2 millimeters thick.

The function of your skin is to:

  • protect your body from environmental stressors like germs, pollution, radiation from the sun, and more
  • regulate your body temperature
  • receive sensory information
  • store water, fat, and vitamin D

But, according to a 2018 article, the interstitium may now be the largest organ. Their findings, which classify the interstitium as an organ, suggest that it might be bigger than the skin.

More than half of your body’s fluid is located in your cells. About a seventh of your body’s fluid is found in the lymph nodes, lymph vessels, heart, and blood vessels. The rest of the fluid is called interstitial fluid.

The interstitium is a series of fluid-filled spaces made of flexible connective tissue. This network of tissue is sometimes called a lattice or mesh.

It’s found in many parts of your body, including:

  • beneath your skin’s surface
  • in your fascia (connective tissue that holds your body together)
  • in the lining of your lungs and digestive tract
  • in the lining of your urinary system
  • surrounding your arteries and veins

It’s well-established that the interstitium is the body’s main source of lymph fluid. However, the study’s authors believe it also protects tissue from the natural movement of your organs, like when your GI tract contracts while digesting food.

They say it may also have a role in conditions like cancer and inflammatory diseases.

Due to these findings, the authors say the interstitium’s unique function makes it an organ. But not all scientists agree.

If the medical community decides it’s an organ, it would be the 80th and largest organ in the body.

Until the 2018 report, the interstitium hadn’t been extensively studied. More research is needed to fully understand the interstitium, as well as its function and overall size.

The largest solid internal organ is your liver. It weighs approximately 3–3.5 pounds or 1.36–1.59 kilograms and is about the size of a football.

Your liver is located beneath your rib cage and lungs, in the upper right area of your abdomen. It works to:

  • filter and eliminate toxins from your blood
  • produce bile
  • make proteins for blood plasma
  • turn excess glucose into glycogen for storage
  • manage blood clotting

At any given moment, your liver is holding approximately one pint of your body’s blood.

Organ size depends on your age, gender, and overall health. But in general, the following organs are the largest internal organs after the liver:


The human brain weighs about 3 pounds or 1.36 kilograms. It’s about the same size as two clenched fists.

The approximate size dimensions of the brain are as follows:

  • Width: 5.5 inches or 14 centimeters
  • Length (front to back): 6.5 inches or 16.7 centimeters
  • Height: 3.6 inches or 9.3 centimeters

Your brain is like your body’s computer. It processes information, interprets sensations, and controls behavior. It also regulates how you think and feel.

Your brain is divided into two halves, which are connected by nerve fibers. Each half of the brain controls specific functions.

Often, the brain’s appearance is compared to that of a supersized walnut. It contains about 100 billion neurons and 100 trillion connections, which send signals to each other and throughout the body.

Your brain is always working and processing information, even when you’re sleeping.


Your lungs are the third largest organs in your body.

  • Together, your lungs weigh approximately 2.2 pounds or about 1 kilogram.
  • They’re about 9.4 inches or 24 centimeters in height during normal breathing.

On average, an adult male’s lungs can hold roughly 6 liters of air. This is about as much as three 2-liter soda bottles.

When you inhale, your lungs oxygenate your blood. When you exhale, they release carbon dioxide.

Your left lung is slightly smaller than your right lung which allows space for the heart. Together, the lungs’ surface area is as big as a tennis court.


After the lungs, the next biggest organ is your heart.

The average heart is:

  • 4.7 inches or 12 centimeters long
  • 3.3 inches or 8.5 centimeters wide
  • about the same size as two hands clasped together

Your heart is situated between your lungs, positioned slightly to the left.

Your heart works with your blood vessels to pump blood throughout your body. Arteries take blood away from your heart and veins bring blood to it. Together, these blood vessels are about 60,000 miles long.

In just 1 minute, your heart pumps 1.5 gallons of blood. The blood is delivered to every cell in your body except the cornea in your eyes.


Your kidneys are the fourth largest organ in your body.

An average kidney is about 10 to 12 centimeters, or 4 to 4.7 inches long. Each kidney is roughly the size of a small fist.

Your kidneys are located at the bottom of your rib cage, one on each side of your spine.

Each of your kidneys contains about 1 million filtering units. When blood enters your kidneys, these filters work to remove waste products, regulate your body’s salt levels, and produce urine.

In just 24 hours, your kidneys filter approximately 200 quarts of fluid. About 2 quarts of this is eliminated from your body as urine.

The interstitium is a network of fluid-filled spaces supported by a mesh of connective tissue. If the medical community accepts it as an organ, it may be the largest organ in your body.

But until then, the skin is at the top of the list as the largest organ. The biggest solid internal organ is your liver, followed by your brain, lungs, heart, and kidneys.