Calculating Density Altitude
(by Oliver Hanisch • oliver@oliverhanisch.com • 310 980 6330)
To calculate DA start by figuring out the PA, which is Pressure Altitude.
The following calculation will compare standard pressure to the actual pressure at sea level to find out
if the air is more dense or less dense than on a standard day.
Pressure Altitude Calculation
1. 29.92 minus the current reported altimeter setting at your field (from ATIS, AWOS,
ASOS, Metars)
2. Take the result and multiply it by 1,000 ft. (since the air pressure is decreasing 1” per
1,000 feet with an increase in altitude)
3. Take that result and add it to your field elevation. (CRG=41 ft.)
4. The result of that is called “PA” which is pressure altitude.
Then we need to find out how much the actual temperature at your elevation is differing from
what standard temperature would be at your elevation.
Let’s call that the temperature diversion.
1. Field elevation multiplied by .002° C (with every 1 foot of altitude increase, the air is getting
two thousandths of a degree colder. 2°C per 1,000 ft.)
2. Now subtract the result from 15° C. (since this is where we start at a standard day)
3. This result is what the temperature would be at your elevation on a standard day.
4. Take this result and subtract it from the actual temperature at your elevation.
This now is the temperature diversion.
5. Take the temperature diversion and multiply it by 120 ft.
6. This is now the density decrease expressed in feet. (If temperature is above standard)
7. Take this result and add it to pressure altitude and you’ll get density altitude (DA)
Short formula:
Pressure Altitude:
1. 29.92 – Current Altimeter = A
2. A x 1,000 = B
3. B + Field Elevation = PA
Density Altitude:
1. Field Elevation x .002 = X
2. 15 – X = Std. temp.
3. Current temperature – Std. temp. x 120 ft = performance loss in feet.
4. Add performance loss in feet to PA = DA
Density Altitude [DA] = Pressure Altitude corrected for non standard temperature.
Density altitude is the altitude at which the aircraft is operating in regards to the density of the air
found at that stated altitude on a standard day. The aircraft can actually be several thousand feet
lower but it operates as it is flying as high as expressed in the DA on a standard day.
Pressure Altitude [PA] = The altitude in reference to standard pressure.
If the pressure is not standard at sea level, the air is more or less dense than on a standard day.
This is expressed as an increase or decrease in altitude. (Indicated altitude if Kollsman window is set
to 29.92)
True Altitude = The altitude above mean sea level.
(Indicated altitude if Kollsman Window is set to proper reported altimeter setting)
Standard Atmosphere
At sea level when the pressure is 29.92 inches of mercury (in. Hg.) or 1013.2 millibars and a
temperature of 15 degrees C or 59 degrees Fahrenheit.
Standard lapse rates
Pressure and temperature normally decreases as altitude increases:
 The standard lapse rate for pressure is approximately 1 inch for each 1,000 feet.
 The standard lapse rate for temperature is 2 degrees C (3.5 degrees F) for every 1,000 feet.