Altitude
Altitude pressure and oxygen explorer
See how standard atmospheric pressure and oxygen partial pressure fall with elevation. The calculation explains the physics of altitude; it does not predict an individual's symptoms or acclimatization.
What the model calculates
The tool uses the standard-atmosphere barometric relationship for the lower atmosphere. It estimates total air pressure at the elevation you enter, then multiplies that pressure by the approximate dry-air oxygen fraction of 20.95% to illustrate oxygen partial pressure.
Why oxygen feels scarcer even though its percentage stays similar
The proportion of oxygen in dry air remains close to 20.95% through the elevations relevant to mountaineering. What falls is atmospheric pressure. With fewer air molecules packed into each breath, the partial pressure that drives oxygen into the body also falls.
Limitations
Actual atmospheric pressure changes with weather and temperature. The simple oxygen partial-pressure value also does not account for humidification in the airways or human physiology. Do not use this calculation to diagnose altitude illness, determine medication or decide whether a person can safely ascend.
Read the altitude and acclimatization guide ยท Check a sleeping-elevation plan