Pressure Altitude Calculator
Calculate pressure altitude from field elevation and altimeter setting. Foundation for density altitude and performance calculations.
About this calculator
Pressure altitude is the altitude in the standard atmosphere at which the standard pressure equals your actual local station pressure -- it is the foundation every aircraft performance chart, and density altitude calculation after it, is built on. This calculator applies the standard aviation rule of thumb that altimeter setting error converts to altitude at roughly 1,000 feet per inch of mercury: for every 0.01 inHg the current altimeter setting sits below the standard 29.92 inHg, pressure altitude rises about 10 feet above field elevation, and vice versa when the setting is above standard. This is why pilots colloquially say "high to low, look out below" -- flying from a region of high pressure into low pressure without resetting the altimeter makes the true pressure altitude higher (and the aircraft actually lower) than the altimeter indicates.
The calculator also derives the International Standard Atmosphere (ISA) temperature expected at that pressure altitude, using the standard 2°C-per-1,000-foot lapse rate from a 15°C sea-level baseline, and estimates atmospheric pressure at that altitude using the standard barometric formula. This tool computes pressure altitude only -- density altitude, which also factors in actual (not standard) temperature and is what actually governs engine and aerodynamic performance, requires a separate calculation using both this pressure altitude and the actual outside air temperature.
Inputs
Sea level to ~14,000 ft for US airports
Typical: 29.82–30.12 inHg
Results
Pressure Altitude
5,000 ft
≈ 5 Eiffel Towers
How to Use This Calculator
- Enter your airport's field elevation from the sectional chart or airport directory.
- Enter the current altimeter setting from ATIS, AWOS, or METAR.
- The result is your pressure altitude — use it in POH performance charts.
How the result changes across these scenarios
| Scenario | Pressure Altitude |
|---|---|
| Sea Level Standard | 0 ft |
| Low Pressure Day | 5,400 ft |
| High Pressure Day | 4,500 ft |
What each input means
- Field Elevation
- Airport elevation above mean sea level. Found on sectional charts or airport facility directory (AFD).
- Altimeter Setting (QNH)
- Current altimeter setting in inches of mercury from ATIS, AWOS, or METAR. Standard is 29.92 inHg.
What each result means
- Pressure Altitude
- Use this value for POH performance chart lookups.
- Pressure Correction
- Altitude correction applied for non-standard pressure.
- ISA Temperature at PA
- Standard temperature at this pressure altitude.
- Atmospheric Pressure
- Estimated atmospheric pressure at this pressure altitude, in inches of mercury -- the unit US pilots use for altimeter settings.
- Atmospheric Pressure
- Estimated atmospheric pressure at this pressure altitude, in hectopascals (the metric/ICAO unit).
How this is calculated
Worked example, using the default values
- Pressure CorrectionCorrection = (29.92 − Altimeter Setting) × 1000(29.92 − 29.92) × 1000 = 0 ft
- Pressure AltitudePA = Field Elevation + Correction5,000 + 0 = 5,000 ft
- ISA Temperature at PAISA Temp = 15°C − 2°C × (PA ÷ 1000)15 − 2 × (5,000 ÷ 1000) = 5.0°C (41.0°F)
Engine last updated . Checked against 1 independently-derived test — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does a lower altimeter setting produce a higher pressure altitude?
A lower altimeter setting means the current atmospheric pressure at your location is below the 29.92 inHg standard, which happens when you're effectively sitting in a column of "thinner," lower-pressure air than standard. Since pressure altitude asks "at what altitude in the standard atmosphere does this same pressure occur," a lower local pressure corresponds to a higher altitude in the standard atmosphere -- which is why the correction adds to field elevation rather than subtracting from it when the altimeter setting is below 29.92.
Why is pressure altitude the foundation for performance charts instead of field elevation?
Aircraft performance -- takeoff roll, climb rate, service ceiling -- depends on actual air density, which in turn depends on both altitude and atmospheric conditions, not on raw field elevation alone. Pilot operating handbook performance charts are built using pressure altitude (and often density altitude, which further adjusts for temperature) specifically because it captures the actual pressure environment the aircraft is flying in, which field elevation by itself does not.
What is the difference between pressure altitude and density altitude?
Pressure altitude, which this calculator computes, corrects field elevation only for non-standard atmospheric pressure. Density altitude goes a step further and also corrects for non-standard temperature, since air density -- what actually governs engine power output, propeller efficiency, and wing lift -- depends on both pressure and temperature together. On a hot day, density altitude can run substantially higher than pressure altitude even when pressure altitude itself is modest.
Why does ISA temperature decrease as pressure altitude increases?
The International Standard Atmosphere model defines a fixed temperature lapse rate of about 2°C per 1,000 feet, reflecting the real average cooling trend of the atmosphere with altitude in the troposphere. This calculator applies that same lapse rate starting from the ISA sea-level standard of 15°C, so a higher pressure altitude always corresponds to a colder expected standard temperature in this model, independent of the actual temperature at your location.
Does this calculator need the actual outside air temperature?
No -- pressure altitude depends only on field elevation and altimeter setting, not on actual temperature. The ISA temperature this calculator reports is the standard-atmosphere EXPECTED temperature at that pressure altitude, not a measurement of real conditions; if you need density altitude, which does depend on actual temperature, that requires a separate calculation combining this pressure altitude with the real outside air temperature.
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