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Pressure Altitude Calculator

Work out pressure altitude instantly with clear inputs, formula shown and shareable results.

About Pressure Altitude Calculator

Pressure altitude is the altitude read on an altimeter set to the standard datum of 1013.25 hPa (29.92 inHg). Each hectopascal below standard raises pressure altitude by roughly 27 ft, so a low pressure day puts the aircraft at a higher pressure altitude than the field elevation suggests.

Formula

Pressure altitude

PA = elevation + (1013.25 - QNH) x 27 ft per hPa

Worked example

With the default values below, Pressure Altitude Calculator returns Pressure altitude of 1,423. Change any input above and every figure here is recalculated in your browser.

Inputs used

Field elevation / indicated altitude
1,200 ft
Altimeter setting (QNH)
1,005 hPa

Results

Pressure altitude
1,423 ft
Altimeter correction
223 ft
Deviation from standard setting
8.25 hPa

Step by step

  1. 1Values used
  2. 2Pressure altitude
  3. 3Pressure altitude= 1,423 ft
  4. 4Altimeter correction= 223 ft
  5. 5Deviation from standard setting= 8.25 hPa

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Aviation results are planning estimates only. Always verify take-off, landing, fuel, weight and balance figures against the certified Aircraft Flight Manual, current performance charts and applicable aviation regulations before flight.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Aviation results are planning estimates only. Always verify take-off, landing, fuel, weight and balance figures against the certified Aircraft Flight Manual, current performance charts and applicable aviation regulations before flight.

Frequently Asked Questions

Why 27 ft per hPa?

Near sea level the atmosphere loses about 1 hPa every 27 ft, so the altimeter's aneroid scale converts pressure setting changes at roughly that rate.

When is pressure altitude the same as elevation?

Only when the altimeter setting is exactly 1013.25 hPa (29.92 inHg), the standard sea-level pressure.

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