Density Altitude Calculator
Calculate density altitude from pressure altitude and outside air temperature using DA = PA + 120 × (OAT − T_ISA).
What Is Density Altitude?
Density altitude is the pressure altitude corrected for non-standard temperature. It reflects how thin the air feels to an aircraft engine and wing. Higher density altitude means reduced engine power and lift.
Density Altitude Formula
$$DA = PA + 120 \times (OAT - T_{ISA})$$\(PA\) is pressure altitude in feet, \(OAT\) is outside air temperature in °C, and \(T_{ISA}\) is the International Standard Atmosphere temperature at that altitude: \(T_{ISA} = 15 - 2 \times (PA/1000)\).
Example: at 5000 ft PA and 25°C OAT, \(T_{ISA} = 5°C\), so \(DA = 5000 + 120 \times 20 = 7400\) ft.
Aviation Impact
Hot days and high airports increase density altitude. Pilots use DA to estimate takeoff roll, climb rate, and service ceiling. Performance charts are often referenced to density altitude rather than field elevation alone.
Frequently Asked Questions
How is pressure altitude different from field elevation?
Pressure altitude is altitude referenced to the standard pressure setting (29.92 inHg). Field elevation is height above mean sea level. They differ when local pressure is non-standard.
Why does hot weather increase density altitude?
Warmer air is less dense. When OAT exceeds ISA temperature, the 120 × (OAT − T_ISA) term adds feet to density altitude, reducing aircraft performance.
What is ISA temperature?
The International Standard Atmosphere assumes 15°C at sea level with a lapse rate of 2°C per 1000 ft. At 5000 ft, ISA temperature is 5°C.
Can density altitude be below pressure altitude?
Yes. When OAT is colder than ISA, density altitude is lower than pressure altitude, which improves aircraft performance.
Is humidity included in this calculation?
This calculator uses the common PA + 120 × (OAT − T_ISA) approximation without humidity correction. Very humid conditions can slightly increase effective density altitude further.
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