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Cited standard/category: Transport & Maritime aviation density altitude

Density Altitude Calculator

Calculate aviation pressure altitude and approximate density altitude from field elevation, altimeter setting, and outside air temperature.

Flight Conditions

Uses the cited Transport & Maritime aviation approximation: pressure altitude = field elevation + (29.92 - altimeter) x 1000, and density altitude = pressure altitude + 120 x (OAT - ISA temperature).

Airport elevation above mean sea level, in feet.
Enter station altimeter in inches of mercury or hectopascals.
Observed temperature at the field.
Recorded for context; the cited approximation does not adjust for humidity.

Results

Results update as inputs change. Verify performance planning against the current aircraft flight manual and current conditions.

Pressure altitude

--

feet

Density altitude

--

feet

ISA temperature

--

deg C at pressure altitude
Enter valid conditions to calculate pressure altitude, density altitude, and performance caution.
Field elevation --
Altimeter normalized --
Outside air temperature --
Temperature deviation from ISA --
Dewpoint context --
Formula basis PA = field elevation + (29.92 - altimeter inHg) x 1000. DA = PA + 120 x (OAT C - ISA C), where ISA C = 15 - 2 x (PA / 1000).

Self-Tests

Golden tests check the pure pressure-altitude and density-altitude formula functions.

Self-tests have not been run.

About the Density Altitude Calculator

Density altitude translates elevation, altimeter setting, outside air temperature, and humidity assumptions into the pressure-altitude equivalent an aircraft feels for performance. Pilots, dispatchers, and instructors use it to brief takeoff distance, climb rate, and engine output risk, especially on hot days at high-elevation airports before comparing the result with the aircraft flight manual.

How it works

  1. Enter airport elevation and current altimeter setting.
  2. Add outside air temperature and humidity if the calculator supports it.
  3. Review pressure altitude and calculated density altitude.
  4. Compare the result with the aircraft performance charts before departure.

Frequently asked questions

What is density altitude in plain English?

It is pressure altitude corrected for nonstandard temperature, with humidity sometimes included as a refinement. It tells pilots how the air density affects aircraft performance.

How do I estimate pressure altitude from altimeter setting?

A common approximation is pressure altitude equals field elevation plus 1,000 ft for each inch Hg that the altimeter setting is below 29.92, or minus that amount when it is above 29.92.

Why does high density altitude reduce performance?

Less dense air reduces wing lift, propeller thrust, and normally aspirated engine power. The result can be longer takeoff roll, slower climb, and reduced obstacle clearance.

Can density altitude be lower than airport elevation?

Yes. Cold temperatures and high pressure can make the air denser than standard, producing a density altitude below field elevation.

Should I use density altitude instead of the POH charts?

No. Use density altitude as an input or briefing aid, then apply the aircraft flight manual or pilot operating handbook performance charts and required safety margins.

References