Density Altitude Calculator
Enter airfield elevation, QNH and outside air temperature to see how hot, high and humid conditions affect performance.
Formula
Pressure altitude ≈ elevation + (1013.25 − QNH) × 27 ft. ISA temp = 15 − 1.98 °C per 1,000 ft. Density altitude ≈ pressure altitude + 120 × (OAT − ISA). This is the common rule-of-thumb approximation.
FAQ
Why does density altitude matter?
Higher density altitude means thinner air: longer takeoff roll, weaker climb and higher true airspeed for the same indicated airspeed.