MasterTool

Pressure Altitude Calculator

Calculate pressure altitude with the standard wind-triangle / ISA formulas.

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What this tool does

Calculate pressure altitude with the standard wind-triangle / ISA formulas. ISA formula rather than the rough 1,000 ft-per-inch rule, which overstates the correction (it would give 5,500 ft for the default example instead of about 5,470 ft). Pressure altitude is the altitude in the standard atmosphere at the same pressure — it is not density altitude, which also needs temperature.

How to use the Pressure Altitude Calculator

  1. Enter or select field elevation (ft).
  2. Enter or select altimeter setting (inhg).
  3. Read the calculated result; change any measurement to compare alternatives.

Formula

ISA sea-level correction: pressure altitude = field elevation + 145366.45 × (1 − (altimeter setting ÷ 29.92126)^0.190284)
elevation
Field elevation (ft)
altimeter
Altimeter setting (inHg)

ISA formula rather than the rough 1,000 ft-per-inch rule, which overstates the correction (it would give 5,500 ft for the default example instead of about 5,470 ft). Pressure altitude is the altitude in the standard atmosphere at the same pressure — it is not density altitude, which also needs temperature.

Worked example

For pressure altitude calculator, the following measurements illustrate the exact method: Field elevation (ft): 5000; Altimeter setting (inHg): 29.42.

Inputs

  • Field elevation (ft)5000
  • Altimeter setting (inHg)29.42

Result

  • Pressure altitude (ft)5,466.57
  • Correction to add to field elevation (ft)466.57
  • Altimeter setting (hPa)996.28

Results explained

Pressure altitude (ft)
Pressure altitude (ft) from the formula above. ISA formula rather than the rough 1,000 ft-per-inch rule, which overstates the correction (it would give 5,500 ft for the default example instead of about 5,470 ft). Pressure altitude is the altitude in the standard atmosphere at the same pressure — it is not density altitude, which also needs temperature.
Correction to add to field elevation (ft)
Correction to add to field elevation (ft) from the formula above. ISA formula rather than the rough 1,000 ft-per-inch rule, which overstates the correction (it would give 5,500 ft for the default example instead of about 5,470 ft). Pressure altitude is the altitude in the standard atmosphere at the same pressure — it is not density altitude, which also needs temperature.
Altimeter setting (hPa)
Altimeter setting (hPa) from the formula above. ISA formula rather than the rough 1,000 ft-per-inch rule, which overstates the correction (it would give 5,500 ft for the default example instead of about 5,470 ft). Pressure altitude is the altitude in the standard atmosphere at the same pressure — it is not density altitude, which also needs temperature.

Frequently asked questions

Pressure altitude = field elevation + 145366.45 × (1 − (altimeter setting ÷ 29.92126)^0.190284), the ISA relation. For a 5,000 ft field with an altimeter setting of 29.42 inHg the correction is about +470 ft, giving a pressure altitude of about 5,470 ft.

That cockpit rule of thumb overstates the correction away from standard pressure: (29.92 − 29.42) × 1,000 = 500 ft, versus about 470 ft from the ISA formula used here, because one inch of mercury is worth about 934 ft near sea level in the standard atmosphere, not exactly 1,000 ft.

Pressure altitude corrects only for non-standard pressure. Density altitude also corrects for non-standard temperature (and, in detailed models, humidity) — it is the altitude that matches the actual air density, and it is what aircraft performance charts really depend on. Use the Density Altitude Calculator for that.

Whenever the altimeter setting is below the standard 29.92 inHg (a low-pressure day): the correction is positive, so pressure altitude sits above the field. On a high-pressure day (setting above 29.92) pressure altitude is below field elevation.

Above the transition altitude everyone flies on the standard setting, so all altimeters share the same pressure reference and vertical separation is consistent. Heights then are flight levels — pressure altitudes in hundreds of feet — rather than altitudes above sea level.