What is the unit of measurement for pressure altitude?

Pressure altitude is measured in feet above sea level (ASL). This unit is derived from the standard atmospheric pressure, which is typically defined as 29.92 inches of mercury (Hg) at sea level. When determining pressure altitude, pilots reference the altimeter set to this standard atmospheric pressure. This measurement is particularly significant because it helps pilots understand their altitude in relation to standard conditions, which is critical for navigation, air traffic control, and flight safety.

Key to interpreting pressure altitude is recognizing that it provides a consistent reference point that is essential for aerodynamic calculations and flight operations. While pressure altitude can also be reported in other units, feet ASL is the conventionally accepted standard in aviation, making it the correct answer in this context.