Altitude Oxygen Calculator

How to Use This Calculator

1. Enter altitude in feet or meters.
2. See atmospheric pressure (mbar and atm), partial O₂ pressure (mmHg), and effective oxygen %.
3. Use Common Cities to look up Denver, Mexico City, Lhasa, La Paz, or Everest.
4. Use Aviation Cabin Altitude to model commercial flight conditions.
5. Switch to Professional for hypoxia risk and FAA supplemental oxygen rules.

Formula

Example

Frequently Asked Questions

• Why does oxygen feel thin at altitude? ▼
  The percentage of oxygen in air (20.9%) stays constant, but atmospheric pressure drops with altitude. Lower pressure means each breath delivers fewer oxygen molecules. At 18,000 ft, pressure is roughly half sea-level, giving the equivalent of only ~10.5% oxygen at sea level.
• What altitude causes AMS (acute mountain sickness)? ▼
  AMS can begin at 8,000 ft in susceptible individuals. Significant symptoms typically onset above 10,000 ft. Severe AMS/HACE/HAPE risk rises sharply above 14,000 ft.
• What is FAA supplemental oxygen policy? ▼
  FAA regulations require pilots to use supplemental oxygen if flying above 12,500 ft MSL for more than 30 minutes, above 14,000 ft at any time, and above 15,000 ft all passengers must be provided oxygen.
• What is time of useful consciousness (TUC)? ▼
  TUC is how long a person can perform useful tasks at altitude without supplemental oxygen. At 25,000 ft it is ~3–5 minutes; at 40,000 ft it drops to 15–30 seconds — why aircraft decompression is a critical emergency.

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