Skip to content

Atlas/ Tools/ Density Altitude

Calculator · Performance

Density altitude.

Pressure altitude + ISA deviation. The number that decides whether your runway is long enough and your climb out clears the trees.

High humidity adds ~50 ft per 5°C dewpoint above 0°C. Leave blank to ignore.

Methodology.

  • · Pressure altitude: PA = elev + (29.92 − altimeter) × 1,000
  • · ISA temperature at PA: ISA = 15 − 2 × (PA / 1,000) °C
  • · Density altitude: DA = PA + 120 × (OAT − ISA)
  • · Humidity correction: +10 × max(0, dewpoint) ft (rough — useful as a flag, not a number to bet on)

Same math the FAA Pilot's Handbook of Aeronautical Knowledge uses (Chapter 11). Aircraft performance numbers in your POH are at the DA you calculate here, not the field elevation.