Pressure Altitude Calculator
Find pressure altitude from field elevation and altimeter setting, in inHg or hPa, using the standard FAA aviation formula.
✈️ What is Pressure Altitude?
Pressure altitude is the altitude an aircraft's altimeter would show if it were set to the standard datum pressure of 29.92 inHg (1013.25 hPa), instead of the actual local altimeter setting. It represents the height above a theoretical standard-pressure reference surface rather than true height above sea level, and it changes as local barometric pressure changes even if the aircraft never moves vertically.
Pilots and flight planners use pressure altitude constantly, as the required starting point for computing density altitude and its effect on engine, propeller, and wing performance, to correct indicated airspeed toward true airspeed at cruising altitudes, to read aircraft performance charts (takeoff distance, climb rate, service ceiling) that are built around standard-pressure reference conditions, and above the transition altitude, as the altitude reference all aircraft use once altimeters are set to 29.92 inHg for consistent vertical separation.
A common misconception is that pressure altitude is the same as the field elevation printed on an airport diagram. It is not, field elevation is a fixed, surveyed number, while pressure altitude shifts continuously with the current altimeter setting. On a low-pressure day, pressure altitude can be meaningfully higher than field elevation even though the airport itself has not moved.
This calculator applies the standard FAA formula directly: pressure altitude equals field elevation plus 1,000 feet for every inch of mercury the altimeter setting sits below the standard 29.92 inHg, and it accepts altimeter settings in either inHg or hPa.
📐 Formula
Per the FAA Pilot's Handbook of Aeronautical Knowledge, this is the standard formula used throughout U.S. flight training and operations to compute pressure altitude from field elevation and altimeter setting.
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 — Standard Day
Field elevation = 1000 ft, altimeter setting = 29.92 inHg
Example 2 — Low-Pressure Day (inHg)
Field elevation = 5000 ft, altimeter setting = 29.50 inHg
Example 3 — Altimeter Setting in hPa
Field elevation = 2000 ft, altimeter setting = 1005.0 hPa
❓ Frequently Asked Questions
🔗 Related Calculators
What is pressure altitude?
Pressure altitude is the altitude indicated when an aircraft's altimeter is set to the standard datum pressure of 29.92 inHg (1013.25 hPa), rather than the actual local altimeter setting. It is the height above a theoretical standard pressure surface, not necessarily true height above sea level.
How do you calculate pressure altitude?
PA (ft) = field elevation (ft) + (29.92 - altimeter setting in inHg) x 1000. If the local altimeter setting is below standard (29.92), pressure altitude is higher than field elevation, if it is above standard, pressure altitude is lower.
Why is pressure altitude important for pilots?
Pressure altitude is the starting point for computing density altitude, true airspeed corrections, and aircraft performance figures like takeoff distance and climb rate, since aircraft performance charts are built around standard-pressure reference conditions.
How do you convert hPa to inHg for this calculator?
Divide the pressure in hectopascals by 33.8639 to get inches of mercury. For example, 1013.25 hPa divided by 33.8639 is approximately 29.92 inHg, the standard atmospheric pressure at sea level.
What altimeter setting gives a pressure altitude equal to field elevation?
When the altimeter setting equals the standard value of 29.92 inHg (1013.25 hPa), pressure altitude equals field elevation exactly, since the (29.92 - altimeter setting) term becomes zero.
Does a low altimeter setting increase or decrease pressure altitude?
A low altimeter setting (below 29.92 inHg) increases pressure altitude above field elevation, since low pressure corresponds to thinner air that behaves as if the aircraft were higher up in the standard atmosphere.
Is pressure altitude the same as true altitude?
No. True altitude is height above mean sea level. Pressure altitude is height above the standard datum plane (29.92 inHg / 1013.25 hPa). The two are equal only when local pressure and temperature exactly match the standard atmosphere.
What is the difference between pressure altitude and density altitude?
Pressure altitude accounts only for non-standard pressure. Density altitude goes one step further and also accounts for non-standard temperature, giving a more complete picture of how the air actually performs for engine, propeller, and wing performance.
Can pressure altitude be negative?
Yes. At low-elevation airports with an altimeter setting above 29.92 inHg, or at any airport during unusually high-pressure conditions, the calculated pressure altitude can come out below zero, meaning it is below the standard datum plane.
Where do I find the current altimeter setting for an airport?
Current altimeter settings are broadcast in METAR weather reports (as inHg in North America, hPa/QNH in most other regions), ATIS recordings, and from air traffic control or flight service.