Pressure Altitude Calculator
Our meteorology & atmospheric science calculator computes pressure altitude accurately. Enter measurements for results with formulas and error analysis.
Formula
PA = 44330 * (1 - (P/1013.25)^0.1903)
Where PA is pressure altitude in meters and P is station pressure in hPa. Density altitude adds temperature correction: DA = PA + 120*(T - ISA_temp). ISA temperature at altitude: T_ISA = 15 - 0.00198*PA.
Worked Examples
Example 1: Sea Level Airport
Problem: Station pressure 1005 hPa, temperature 30 C, elevation 50 ft.
Solution: PA = 44330*(1-(1005/1013.25)^0.1903) PA = 68 m (223 ft) ISA at 68m = 14.9C, deviation = +15.1C DA = 68 + 120*15.1 = 1880 m (6168 ft)
Result: PA: 68 m | DA: 1880 m | Performance Impact
Example 2: Mountain Airport
Problem: Station pressure 850 hPa, temperature 25 C.
Solution: PA = 44330*(1-(850/1013.25)^0.1903) PA = 1457 m (4781 ft) ISA = 12.1C, dev = +12.9C DA = 1457+120*12.9 = 3005 m
Result: PA: 1457 m | DA: 3005 m | High
Frequently Asked Questions
What is pressure altitude and why is it important?
Pressure altitude is the altitude in the standard atmosphere at which the given pressure would be found. It equals 44330*(1-(P/1013.25)^0.1903) meters where P is the actual station pressure. Pressure altitude is fundamental in aviation because aircraft altimeters work by measuring pressure and converting it to altitude using the standard atmosphere model. It determines aircraft performance characteristics including takeoff distance rate of climb and service ceiling. When the altimeter setting is 29.92 inHg the indicated altitude equals pressure altitude.
How does pressure altitude differ from density altitude?
Pressure altitude only accounts for pressure while density altitude additionally corrects for non-standard temperature. Density altitude equals pressure altitude plus approximately 120 times the temperature deviation from ISA in Celsius. Density altitude is the altitude in the standard atmosphere with the same air density as the actual conditions. Aircraft performance charts typically reference density altitude because engine power and wing lift both depend on air density. On hot days density altitude can be thousands of feet above pressure altitude reducing aircraft performance.
How do pilots use pressure altitude?
Pilots use pressure altitude for multiple critical operations. During takeoff and landing they calculate pressure altitude to determine required runway length and climb performance. Above the transition altitude typically 18000 feet in the US all aircraft set altimeters to 29.92 inHg and fly at flight levels based on pressure altitude ensuring safe vertical separation. Pressure altitude determines oxygen requirements with supplemental oxygen required above 12500 feet pressure altitude for extended periods. Performance charts in pilot operating handbooks are indexed to pressure altitude and temperature.
How is pressure altitude related to altimeter settings?
The altimeter setting is the pressure at mean sea level that makes the altimeter read field elevation on the ground. When the altimeter is set to the current local setting it shows elevation not pressure altitude. Setting 29.92 inHg (1013.25 hPa) makes the altimeter display pressure altitude directly. The relationship between station pressure and altimeter setting involves correcting for elevation using the hypsometric equation. A one inHg change in altimeter setting corresponds to approximately 1000 feet of altitude change near sea level.
What factors cause pressure altitude to change?
Pressure altitude changes whenever the station pressure changes which occurs due to weather systems and diurnal pressure variations. Low pressure weather systems raise pressure altitude sometimes by several hundred feet while high pressure systems lower it. Temperature does not directly affect pressure altitude but changes density altitude. Elevation determines baseline station pressure with higher elevation airports having inherently higher pressure altitudes. Seasonal pressure patterns also affect average pressure altitude at a given location.
How does density altitude affect aircraft performance?
Higher density altitude degrades all aspects of aircraft performance because thinner air reduces both engine power output and aerodynamic lift. Takeoff distance increases significantly with density altitude requiring longer runways. Rate of climb decreases which is critical at airports surrounded by terrain. True airspeed increases relative to indicated airspeed requiring adjustment for navigation. Propeller efficiency decreases in thinner air. As a rule of thumb takeoff distance increases about 10 percent for every 1000 feet of density altitude above sea level.