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.
Reviewed by Daniel Agrici, Founder & Lead Developer
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.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy