Pilot calculators › Density altitude
Density altitude calculator
Density altitude is the altitude the airplane "feels". Hot, high and humid air makes it climb above the field elevation, and takeoff and climb performance drop with it.
Calculator
Enter values to see the result.
How it's calculated
First the calculator turns your altimeter setting and elevation into station pressure and pressure altitude, using the formulas the US National Weather Service publishes. Then it works out the air's density from that pressure and the temperature. If you enter a dew point, it adds the moisture, because humid air is lighter. The result is the altitude in the standard atmosphere that has the same air density.
Beside it you'll see the rule of thumb taught in ground school: density altitude ≈ pressure altitude + 120 × (outside temperature − standard temperature), where standard temperature is about 15°C minus 2°C per 1,000 feet. The two agree within a few hundred feet on most days.
What it means for a flight
- Higher density altitude means a longer takeoff roll, a slower climb and less engine power in a normally aspirated airplane.
- Use the inputs your POH or AFM performance charts ask for. Many charts take pressure altitude and temperature separately rather than density altitude, so enter what the chart specifies, not field elevation alone.
- Summer afternoons at high airports are the classic trap, and so are heavy loads on short runways.