# What's the pressure altitude?

Pressure altitude calculator for pilots: the pressure altitude from the field elevation and altimeter setting, or from the station pressure, with the 1,000 ft per inch rule of thumb and the station pressure.

- Page: https://www.acalculator.org/physics/pressure-altitude-calculator
- JSON spec: https://www.acalculator.org/physics/pressure-altitude-calculator.json
- Version: 145a3ef217aa

## Default answer

Example with the default inputs (From Altimeter setting, Field elevation 5,000 ft, Altimeter setting 29.72 inHg): The pressure altitude is 5,187 ft.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| from | From | Work from the field elevation and altimeter setting, or from a station pressure. |
| elev | Field elevation | The elevation of the airport or place, above mean sea level. |
| alt | Altimeter setting | The altimeter setting (QNH) from ATIS, METAR or the tower, such as 29.92 inHg or 1013 hPa. |
| stn | Station pressure | The actual air pressure at the station, not reduced to sea level. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| pa | Pressure altitude | The height in the standard atmosphere with this pressure. |
| rule | Rule of thumb | Elevation + 1,000 ft × (29.92 − altimeter setting in inHg). |
| correction | Altimeter correction | Pressure altitude − field elevation: h(altimeter setting). |
| stationHpa | Station pressure (hPa) | The pressure at the station in hectopascals (millibars). |
| stationInHg | Station pressure (inHg) | The pressure at the station in inches of mercury. |
| isa | ISA temperature (°C) | The standard-atmosphere temperature at this pressure altitude: 15 − 1.9812 per 1,000 ft. |

## Method

h(p) = 145,366.45 × (1 − (p ÷ 1,013.25)^0.190284) ft, p in hPa. From a station pressure: PA = h(p). From an altimeter setting A: PA = elevation + h(A); station pressure = 1,013.25 × (1 − PA ÷ 145,366.45)^(1 ÷ 0.190284). Rule of thumb: elevation + 1,000 × (29.92 − A in inHg).

## Assumptions

- The standard atmosphere: 1,013.25 hPa (29.92 inHg) and 15 °C at sea level, cooling 1.9812 °C per 1,000 ft.
- 1 inHg = 33.8639 hPa (mercury at 0 °C under standard gravity).

## Worked examples

1. from = station, stn = 101,325 gives pa = 0, isa = 15. Source: Wikipedia, Pressure altitude (h = 145,366.45 × [1 − (station pressure in mb ÷ 1,013.25)^0.190284] ft; rule of thumb PA = elevation + 1,000 × (29.92 − altimeter setting)), https://en.wikipedia.org/wiki/Pressure_altitude (retrieved 2026-10-05).
2. from = station, stn = 84,300 gives pa = 1,524.072639. Source: Wikipedia, Pressure altitude (h = 145,366.45 × [1 − (station pressure in mb ÷ 1,013.25)^0.190284] ft; rule of thumb PA = elevation + 1,000 × (29.92 − altimeter setting)), https://en.wikipedia.org/wiki/Pressure_altitude (retrieved 2026-10-05).
3. from = altimeter, elev = 1,524, alt = 100,643.470391 gives pa = 1,580.863735, rule = 1,584.96. Source: Wikipedia, Pressure altitude (h = 145,366.45 × [1 − (station pressure in mb ÷ 1,013.25)^0.190284] ft; rule of thumb PA = elevation + 1,000 × (29.92 − altimeter setting)), https://en.wikipedia.org/wiki/Pressure_altitude (retrieved 2026-10-05).

## FAQ

### How do you calculate pressure altitude?

Add the field elevation to the altitude correction for the altimeter setting. The quick rule is PA = elevation + 1,000 × (29.92 − altimeter setting). At a 5,000 ft field with 29.72 inHg that is 5,000 + 200 = 5,200 ft; the exact formula gives 5,187 ft.

### What is pressure altitude?

It is the altitude your altimeter shows when set to the standard 29.92 inHg (1,013.25 hPa): the height in the standard atmosphere at which the pressure equals the pressure where you are.

### What is the pressure altitude formula?

h = 145,366.45 × [1 − (p ÷ 1,013.25)^0.190284] feet, where p is the station pressure in hectopascals (millibars). This is the formula the US National Weather Service uses.

### Why does the rule of thumb differ from the formula?

The rule assumes 1,000 ft per inch of mercury everywhere. Near sea level the formula gives about 937 ft for the first inch, so the rule overstates the correction a little; the error grows as the setting moves away from 29.92.

### Is pressure altitude the same as density altitude?

No. Pressure altitude corrects only for pressure. Density altitude also corrects for temperature (and humidity), and it is the one that sets aircraft performance.

### What is the difference between altimeter setting and station pressure?

Station pressure is the actual pressure at the field. The altimeter setting is that pressure reduced to sea level, so an altimeter set to it reads the field elevation on the ground.

## Sources

- Wikipedia, Pressure altitude: the NWS formula h = 145,366.45 × [1 − (p ÷ 1,013.25)^0.190284] ft and the rule PA = elevation + 1,000 × (29.92 − altimeter setting), retrieved 2026-10-05. https://en.wikipedia.org/wiki/Pressure_altitude
- National Weather Service, Pressure Altitude Calculator, retrieved 2026-10-05. https://www.weather.gov/epz/wxcalc_pressurealtitude
- NIST Special Publication 811 (2008), Appendix B.8: 1 ft = 0.3048 m; 1 inHg (0 °C) = 3,386.389 Pa, retrieved 2026-10-05. https://www.nist.gov/pml/special-publication-811