What is Pressure Altitude?

Pressure altitude is the height above a standard theoretical atmospheric plane (the standard datum) where the air pressure is 29.92 inches of mercury (inHg) or 1013.25 hectopascals (hPa). In simpler terms, it is the altitude indicated on your altimeter when it is set to the standard barometric pressure of 29.92.

In aviation, pressure altitude is a critical concept because it is used to determine aircraft performance, including takeoff distance, rate of climb, and true airspeed. It serves as the baseline for calculating Density Altitude, which tells pilots how the aircraft will actually perform in the current air density conditions.

How to Use This Calculator

To calculate pressure altitude using our tool, follow these simple steps:

• Elevation: Enter the current field elevation or the height of the aircraft in feet.
• Altimeter Setting: Enter the current local barometric pressure (altimeter setting) provided by ATIS or a local weather station in inches of mercury (inHg).
• Calculate: Click the button to see the result. The calculator uses the standard lapse rate formula of 1,000 feet per 1 inch of mercury deviation.

The Pressure Altitude Formula

The standard mathematical formula used by this calculator is:

PA = Elevation + ((29.92 - Altimeter Setting) × 1000)

If the local pressure is lower than the standard 29.92, the pressure altitude will be higher than the physical elevation. Conversely, if the pressure is higher than standard, the pressure altitude will be lower than the physical elevation.

Frequently Asked Questions

Why is pressure altitude important for pilots?

Pilots use pressure altitude to standardize flight levels above the transition altitude (usually 18,000 feet in the US). It ensures that all aircraft in the high-altitude environment are using the same reference point for vertical separation.

How does it differ from Density Altitude?

While pressure altitude accounts for changes in atmospheric pressure, density altitude also accounts for temperature. On a hot day, density altitude will be much higher than pressure altitude, signifying thinner air and decreased aircraft performance.

When should I use 29.92 inHg?

In the United States, pilots typically set their altimeter to 29.92 when climbing through 18,000 feet MSL (Mean Sea Level). At this point, the altimeter displays pressure altitude rather than indicated altitude above sea level.