Density Altitude Calculator
Pressure altitude corrected for temperature — the altitude your aircraft feels.
Inputs
Result
Density altitude
4,289ft
Above pressure altitude — degraded performance
Pressure altitude
2,008ft
ISA deviation
ISA temp here ≈ 11 °C
+19°C
Density altitude 4,289 ft (ISA +19 °C)
Formula
Ref- PA = elevation + (1013.25 − QNH) × 30 [ft]
- ISA temp = 15 − 2 × (PA ÷ 1000) [°C]
- DA = PA + 120 × (OAT − ISA temp) [ft]
Worked example
RefField 2,000 ft, QNH 1013 hPa, OAT 30 °C.
- 1.Pressure altitude ≈ 2,000 ft (QNH is standard).
- 2.ISA temp at 2,000 ft = 15 − 4 = 11 °C.
- 3.ISA deviation = 30 − 11 = +19 °C.
- 4.DA = 2,000 + 120 × 19 = 4,280 ft.
Density altitude ≈ 4,280 ft — the aircraft performs as if at 4,280 ft.
How it works
RefWarm, low-pressure, high-elevation air is thin. Density altitude expresses that thinness as an equivalent standard-atmosphere altitude. Higher DA means longer take-off runs, reduced climb, and a higher true airspeed for the same indicated — the root of most 'hot and high' performance accidents.
DGCA student tip
ExamRemember the two rules: 30 ft per hPa for the pressure correction and 120 ft per °C of ISA deviation for temperature. Examiners love a field-elevation + non-standard-temp density altitude question.
Common mistakes
Watch- Using field elevation directly instead of first correcting to pressure altitude.
- Recomputing ISA temperature from field elevation rather than pressure altitude.
- Forgetting DA raises true airspeed — indicated stays the same, TAS climbs.