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    Density Altitude Calculator

    Find the pressure altitude and density altitude from the field elevation, altimeter setting and temperature.

    ft
    ResultUpdates as you type—Density altitude—Pressure altitude—ISA temperature there—ISA deviation

    How your density altitude is worked out

    Find how thin the air is, then the standard height with air that thin.

    1. 1

      Pressure altitude

      5,000 ft field
      QNH 29.92 inHg
      → 5,000 ft

    2. 2

      Standard temperature there

      15 − 1.981 × 5.00
      = 5.1 °C

    3. 3

      Compare with the real air

      30 °C − 5.1 °C
      = +24.9 °C

    4. 4

      Density altitude

      Air density 79%
      of ISA sea level
      → 7,800 ft

    Read more: the formulas, the 120 ft rule and a worked example

    Density altitude is the height in the standard atmosphere where the air would be as thin as it is at your airport now. On a hot day, or when pressure is low, the air is thinner. Engines make less power, propellers and wings work less well, and take-off and climb get longer and slower.

    Step 1: pressure altitude

    Pressure altitude is what your altimeter reads with 29.92 inHg (1013.25 hPa) set. A quick rule is to add 1,000 ft for every inch below 29.92, or about 30 ft for every hectopascal below 1013. This calculator uses the exact standard-atmosphere formula.

    PA = 145,442 − (QNH ÷ 1013.25)^0.190263 × (145,442 − elevation)

    Step 2: density altitude

    The air's density comes from the pressure at that altitude and the actual temperature. Density altitude is the standard-atmosphere height with the same density.

    σ = (pressure ratio) ÷ (temperature K ÷ 288.15)
    DA = 145,442 × (1 − σ^0.234969)

    A common shortcut is density altitude ≈ pressure altitude + 120 × (OAT − ISA temperature). It is within a few hundred feet in most conditions.

    Worked example

    An airport at 5,000 ft with 29.92 inHg set has a pressure altitude of 5,000 ft. The ISA temperature there is about 5 °C. At 30 °C it is about 25 °C warmer than standard, and the density altitude is about 7,800 ft. The aircraft will perform as if it were nearly 3,000 ft higher.

    Assumes dry air; humid air is slightly less dense, so real density altitude can be a little higher. For planning and education. Always use your aircraft's approved performance charts for operational decisions.