What Is the Largest Organ in the Human Body?
Your skin covers every surface you have — and it qualifies as a full organ. Here is how it compares to the liver and why that matters in everyday health.
The skin is the largest organ in the human body — about 20 square feet in adults and roughly 16% of body weight. The liver is the largest internal organ.
Most people name the heart, brain, or liver when asked about the body's largest organ. The answer that surprises many quiz-takers is the skin — a continuous organ that wraps the entire body, regulates temperature, and forms the first barrier against infection.
Skin Counts as an Organ
An organ is a group of tissues working together for a shared function. Skin includes the epidermis, dermis, and underlying structures that sense touch, produce vitamin D with sunlight, and heal after injury.
Spread flat, adult skin covers roughly 20 square feet and accounts for about 16% of body weight — larger and heavier than the liver, which is the biggest internal organ.
Key Facts
Skin renews constantly: the outer layer replaces itself over weeks, which is why shallow cuts heal without leaving deep scars.
It holds roughly two million sweat glands and a rich network of nerves — especially on the face, palms, and soles.
Sun protection, gentle cleansing, and prompt care for wounds support this organ across a lifetime.
References
National Cancer Institute — SEER training modules on skin structure (NIH).
MedlinePlus — Skin anatomy (U.S. National Library of Medicine).
American Academy of Dermatology — public education on skin health.
Key Takeaways
- An organ is a group of tissues working together for a shared function.
- Skin renews constantly: the outer layer replaces itself over weeks, which is why shallow cuts heal without leaving deep scars.
- National Cancer Institute — SEER training modules on skin structure (NIH).
Frequently Asked Questions
Is skin really an organ?
Yes. It is an organ system made of multiple tissue types with defined roles in protection, sensation, and temperature control.
What is the largest internal organ?
The liver — it processes nutrients, filters blood, and supports many metabolic functions.
Does skin weight change with age?
Thickness and elasticity change over time, but skin remains the largest organ by surface area throughout adulthood.
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