Station Pressure to Pressure Altitude Calculator
Calculate station pressure pressure altitude with our free science calculator. Uses standard scientific formulas with unit conversions and explanations.
Formula
PA = 44330 * (1 - (Ps/1013.25)^0.1903)
Where PA is pressure altitude in meters and Ps is station pressure in hPa. DA = PA + 120*(T-ISA_temp) for density altitude.
Worked Examples
Example 1: Elevated Airport
Problem: Station pressure 985 hPa, elevation 300 m, temperature 20 C.
Solution: PA = 44330*(1-(985/1013.25)^0.1903) = 241 m ISA = 14.5C, dev = +5.5C DA = 241+120*5.5 = 901 m
Result: PA: 241 m | DA: 901 m
Example 2: Hot Day Low Pressure
Problem: Station pressure 1000 hPa, temperature 38 C.
Solution: PA = 112 m ISA = 14.8C, dev = +23.2C DA = 112+120*23.2 = 2896 m
Result: PA: 112 m | DA: 2896 m | High
Frequently Asked Questions
How do you convert station pressure to pressure altitude?
Station pressure converts to pressure altitude using the standard atmosphere formula: PA = 44330*(1-(Ps/1013.25)^0.1903) meters where Ps is station pressure in hPa. This formula derives from integrating the hydrostatic equation with the standard atmosphere temperature lapse rate of 6.5 C per kilometer. The result gives the altitude in the ISA model where that pressure would naturally occur. For quick estimates near sea level every 1 hPa decrease from 1013.25 hPa adds approximately 8.3 meters or 27.3 feet to pressure altitude.
What is the difference between station pressure and sea level pressure?
Station pressure is the actual atmospheric pressure measured at the station elevation while sea level pressure (SLP) is station pressure corrected to mean sea level using the hypsometric equation. Weather maps show SLP to enable comparison between stations at different elevations. The correction assumes a standard temperature profile between the station and sea level. Station pressure is what aircraft altimeters actually measure while SLP is what pilots receive as the altimeter setting converted from the QNH value.
Why is station pressure more useful than QNH for pressure altitude?
Station pressure gives pressure altitude directly through the standard atmosphere equation without any intermediate corrections. QNH is sea-level corrected pressure used to make altimeters read elevation on the ground. To get pressure altitude from QNH you must first reverse the sea level correction to obtain station pressure then apply the standard atmosphere formula. Using station pressure eliminates this extra step and its associated assumptions about the temperature profile between the station and sea level.
What is the standard sea level pressure and why does it matter?
Standard sea level pressure is 1013.25 hPa (29.9212 inHg) as defined by the International Standard Atmosphere. This value serves as the reference point for all pressure altitude calculations. When actual sea level pressure differs from standard the altimeter will show pressure altitude that differs from true altitude. For every hPa above standard the true altitude is about 8 meters higher than indicated. This is why pilots must set the correct altimeter setting to maintain accurate altitude indications below the transition altitude.
How do automated weather stations report station pressure?
Automated stations measure atmospheric pressure using precise digital barometers. The raw measurement is station pressure at sensor elevation. The station then computes altimeter setting and sea level pressure using known elevation and temperature. In METAR reports the altimeter setting appears in the A group as four digits in inches of mercury. Station pressure may be available through supplementary data queries from the automated observation system.
How is pressure altitude used in flight planning?
Flight planners calculate pressure altitude to determine aircraft performance for every flight phase. Takeoff distance and initial climb gradient depend on pressure altitude and temperature. En route cruise performance and fuel consumption depend on pressure altitude at the planned flight level. Landing calculations use destination pressure altitude for required distance. Emergency scenarios require single-engine service ceiling relative to terrain expressed as pressure altitude.