---
title: "Skin — what it does and the numbers"
description: "The largest organ — about 2 m² and 4 kg in an adult. What it does, where it is, the figures people look up, and the widely repeated claims that turn out to be wrong."
url: https://atoneplace.net/body/skin/
site: "At One Place"
---

# Skin

**Skin: The largest organ — about 2 m² and 4 kg in an adult.**

Provides a barrier against pathogens and water loss, regulates temperature through sweat and blood flow, synthesises vitamin D, and carries the sense of touch, pressure, temperature and pain.

## Where it is

The entire external surface.

## The numbers

- **Area:** 1.5–2.0 m²
- **Mass:** about 4 kg, or 16% with fat
- **Thickness:** 0.5 mm on eyelids to 4 mm on soles
- **Full renewal:** about 4 weeks

## Worth knowing

The outermost layer is entirely dead cells, replaced roughly every four weeks, and a substantial fraction of household dust is shed skin. Skin colour comes from melanin produced by melanocytes, and everyone has approximately the same number of melanocytes — what differs is how much melanin they produce.

> Structural reference only — this is not medical advice, and individual variation in every figure here is substantial. Anything concerning your own health belongs with a clinician rather than a reference page.

## Common questions

### What does the skin do?

Provides a barrier against pathogens and water loss, regulates temperature through sweat and blood flow, synthesises vitamin D, and carries the sense of touch, pressure, temperature and pain..

### Skin — key numbers

Area: 1.5–2.0 m². Mass: about 4 kg, or 16% with fat. Thickness: 0.5 mm on eyelids to 4 mm on soles. Full renewal: about 4 weeks.

## Related pages

- [Heart](https://atoneplace.net/body/heart/)
- [Brain](https://atoneplace.net/body/brain/)
- [Liver](https://atoneplace.net/body/liver/)
- [Lungs](https://atoneplace.net/body/lungs/)
- [Kidneys](https://atoneplace.net/body/kidneys/)
- [Bones](https://atoneplace.net/body/bones/)
- [Blood types](https://atoneplace.net/body/blood-types/)
- [Teeth](https://atoneplace.net/body/teeth/)
- [Blood](https://atoneplace.net/body/blood/)
- [The senses](https://atoneplace.net/body/senses/)
- [Taste](https://atoneplace.net/body/taste/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)