Approximately what percentage of dry air by volume is nitrogen?

Concept

Atmospheric composition is commonly expressed as a percentage by volume. In dry air, the major gases account for nearly all the total volume, while water vapour is excluded because its amount varies.

Application

Nitrogen makes up about 78.08% of dry air by volume. Rounding this standard value to the nearest whole percent gives 78%.

Contrast and cross-check

• 21.5% is close to the share of oxygen, not nitrogen.

• 40% is far below nitrogen’s dominant share and far above the oxygen share.

• 3% would describe only a small component, whereas nitrogen is the principal gas in dry air.

A quick total check is that about 78% nitrogen plus about 21% oxygen gives roughly 99%; argon, carbon dioxide, and other trace gases make up most of the remainder.

Result

Therefore, the approximate percentage of nitrogen in dry air is 78%.