Density Altitude
Last updated: April 20, 2026 · Maintained by Aviatr Editorial Team
What is Density Altitude?
Density altitude is pressure altitude corrected for non-standard temperature — the altitude the atmosphere 'feels' to the aircraft. High density altitude means thinner air, which reduces engine power, propeller efficiency, and lift, lengthening takeoff roll and significantly reducing climb performance on any given day.
DA = PA + (120 × (OAT − ISA))How is Density Altitude used?
Every pilot computes density altitude before operating from high-elevation or hot-day airports because takeoff distance and single-engine climb performance both degrade sharply as density altitude rises. A Cessna 172 that needs 300 metres of runway at sea level on a cool day can need over 600 metres at 1,500 metres density altitude on a 30 degree Celsius summer day — a difference that turns routine departures into rejected takeoffs on short strips. The rule of thumb is to add about 120 feet of density altitude for every one-degree Celsius above ISA, on top of the pressure altitude. Performance charts in every Pilot's Operating Handbook are indexed by density altitude, and EASA exams test the concept across weather, performance, and procedures subjects for every license from LAPL to ATPL. Mountain flying courses across Europe devote entire ground-school days to density altitude scenarios because alpine airfields routinely see density altitudes above 8,000 feet on hot summer afternoons.