how much oxygen is in the air we breathe

The air we breathe is about 21% oxygen by volume, more precisely around 20.95%.

Quick Scoop

• Oxygen: about 21%.
• Nitrogen: about 78%.
• Other gases: about 1%, including argon, carbon dioxide, and trace gases.

Breathing Detail

The exact oxygen level in inhaled air is close to 21%, but exhaled air usually has less, around 16% to 17%, because your body uses some oxygen during gas exchange.

Simple Example

If you took 100 liters of dry air, roughly 21 liters would be oxygen and about 78 liters would be nitrogen.