What pressure altitude means
Pressure altitude is the altitude indicated when the altimeter is set to the standard pressure of 29.92 inHg. This calculator estimates it from airport field elevation and the local altimeter setting. Pressure altitude is used in aircraft performance calculations and is an input to other planning tools.
Pressure altitude is not necessarily the aircraft's height above the ground or its indicated altitude with the local setting. It describes altitude relative to the standard pressure datum. Temperature is not part of this calculation.
How to use the calculator
Enter the airport's published field elevation in feet above mean sea level and a current altimeter setting in inches of mercury. The result updates as the inputs change, and the inputs are stored in the page URL.
Use a setting from a current aviation weather observation or other appropriate source. Do not use a pressure setting from a different location without considering whether it represents the conditions for the calculation.
How the calculation works
The calculation applies an approximate altitude correction of 1,000 ft for each 1.00 inHg difference between the standard setting and the entered setting:
pressure altitude = field elevation + (29.92 - altimeter setting) x 1,000
When the local altimeter setting is lower than 29.92 inHg, pressure altitude is above field elevation. When the setting is higher, pressure altitude is below field elevation. The result is rounded to the nearest foot for display.
Example calculation
For a field elevation of 5,000 ft and an altimeter setting of 29.42 inHg:
- Setting difference:
29.92 - 29.42 = 0.50 inHg. - Approximate correction:
0.50 x 1,000 = 500 ft. - Pressure altitude:
5,000 + 500 = 5,500 ft.
Assumptions and limitations
The 1,000 ft per inHg correction is a planning approximation. It is not a direct measurement of pressure altitude, and pressure can vary with location and time. This calculator does not account for temperature, aircraft altimeter error, instrument calibration, or pressure changes during a flight.
Use the pressure altitude procedure specified by the relevant aircraft documentation or training material when precision matters. Do not use this estimate alone to make an operational decision.
Sources and methodology
The pressure datum is the standard altimeter setting used in aviation. The FAA Aviation Weather Handbook discusses altimeter settings and pressure. Aircraft-specific performance procedures and limits belong to the current POH or AFM.
Related tools and resources
Flight planning
About this site
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