---
title: "Lungs — what it does and the numbers"
description: "Two unequal lungs with a gas-exchange surface of about 70 square metres. What it does, where it is, the figures people look up, and the widely repeated claims that t"
url: https://atoneplace.net/body/lungs/
site: "At One Place"
---

# Lungs

**Lungs: Two unequal lungs with a gas-exchange surface of about 70 square metres.**

Exchange oxygen and carbon dioxide across roughly 500 million alveoli. Breathing is driven mainly by the diaphragm, and the lungs themselves contain no muscle — they are inflated by the chest cavity expanding around them.

## Where it is

Chest cavity either side of the heart.

## The numbers

- **Alveoli:** about 500 million
- **Gas-exchange surface:** 50–75 m²
- **Breaths per day:** roughly 20,000
- **Tidal volume at rest:** about 500 ml

## Worth knowing

The left lung is smaller than the right and has two lobes rather than three, because the heart occupies space on that side — the cardiac notch is a literal indentation. The alveolar surface is roughly the floor area of a squash court, folded into a space the size of two footballs.

## A common claim that is wrong

Lungs do not "pull" air in. Air is pushed in by atmospheric pressure once the diaphragm lowers and the chest volume increases — which is why a punctured chest cavity stops the lung inflating even though the lung is undamaged.

> 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 lungs do?

Exchange oxygen and carbon dioxide across roughly 500 million alveoli.

### Lungs — key numbers

Alveoli: about 500 million. Gas-exchange surface: 50–75 m². Breaths per day: roughly 20,000. Tidal volume at rest: about 500 ml.

### Is it true that…

Lungs do not "pull" air in. Air is pushed in by atmospheric pressure once the diaphragm lowers and the chest volume increases — which is why a punctured chest cavity stops the lung inflating even though the lung is undamaged.

## Related pages

- [Heart](https://atoneplace.net/body/heart/)
- [Brain](https://atoneplace.net/body/brain/)
- [Liver](https://atoneplace.net/body/liver/)
- [Skin](https://atoneplace.net/body/skin/)
- [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/)