Definition
The altitude shown on an altimeter when its barometric setting is adjusted to the standard sea-level pressure of 29.92 inches of mercury (1013.2 hPa). It represents height above the standard datum plane and is used for high-altitude flight, density altitude calculations, and aircraft performance planning.
Plain English
The altitude you read on the altimeter when you set it to a fixed standard pressure setting (29.92) instead of the local pressure. It gives every aircraft a common reference so they can compare altitudes the same way.
Context Anchor
Seen in aircraft performance, weather, oxygen-use, and night flying discussions, especially where altitude and reduced oxygen can affect night vision.
Derivation
From Latin 'pressura' (a pressing) and 'altitudo' (height). The term literally means 'height measured by pressure' — because altimeters work by sensing the drop in air pressure as you climb, and pressure altitude is the altitude that pressure corresponds to under standard atmospheric conditions.
Why Pilots Care
Provides a standardized reference for aircraft performance data that remains consistent regardless of local barometric pressure.
Grounding Statement
As an airplane climbs, outside air pressure drops, and pressure altitude expresses altitude by that pressure drop.
Intuition Check
Do not read pressure altitude as “the pressure inside the airplane” or as exact height above the ground. It means altitude referenced to a standard air-pressure setting.
Example Sentence 1
Before checking the takeoff performance chart, the pilot set the altimeter to 29.92 to read the field's pressure altitude.
Example Sentence 2
At night the crew checked pressure altitude to determine if supplemental oxygen was required.