Calculating Oxygen Partial Pressure on Mount Everest

Atmospheric pressure decreases with altitude. On Mount Everest's summit, the total atmospheric pressure is roughly one-third of the sea-level value.

At Sea Level

• Total atmospheric pressure = 1 atm
• Oxygen fraction in dry air ≈ 0.21 (21%)
• Partial pressure of O₂ = 0.21 × 1 atm = 0.21 atm

On Mount Everest Summit

• Total atmospheric pressure ≈ ⅓ atm (≈ 0.333 atm)
• Oxygen fraction remains ~0.21
• Partial pressure of O₂ = 0.21 × ⅓ atm = 0.07 atm

Result: The partial pressure of oxygen at the summit of Mount Everest is approximately 0.07 atm, which is exactly one-third of its sea-level value (0.21 atm). This dramatic reduction is the primary physiological challenge for climbers, necessitating acclimatization and often supplemental oxygen.