Estimate

A randomly chosen dry-air particle is oxygen

Probability:
20.9%
Odds:
1 to 3.8
dBan
−5.8 dBan

By particle count, oxygen molecules make up about 21% of the representative dry-air sample.

Calculation

p ≈ 0.2095 by particle count

Assumptions

Under an ideal-gas model, the published dry-air volume fraction equals the particle fraction. Local composition varies.

Sources

  1. NASA Earth Fact Sheet composition updated 15 November 2024