Weather & Climate
Density altitude calculator.
Density altitude is the altitude in the standard atmosphere that has the same air density as your conditions. Enter actual station pressure, temperature and dew point. At 35°C, a 15°C dew point and 24.90 inHg it is about 8,583 ft. Not for flight planning.
Conditions
Density altitude
Fill the form and press Calculate.
Worked example
Station pressure 24.90 inHg (843.2 hPa), air temperature 35°C, dew point 15°C. The vapour pressure at the dew point is 17.06 hPa, so the virtual temperature is 37.4°C, which is 558.9°R. Density altitude = 145,366 × [1 − (17.326 × 24.90 ÷ 558.9)0.235] = about 8,583 ft (2,616 m). A check case: 29.92 inHg, 15°C and a dew point of -60°C gives about 18 ft, close to zero as expected for standard sea-level conditions.
How it works
The calculator follows the US National Weather Service El Paso density altitude calculator. It finds the vapour pressure from the dew point, e = 6.11 × 107.5 Td / (237.3 + Td) hPa, then the virtual temperature Tv = T / [1 − (e / P)(1 − 0.622)] in kelvins, then DA = 145,366 × [1 − (17.326 × PinHg / Tv,Rankine)0.235] feet, where P is the station pressure.
The NWS page asks for the actual station pressure, not the altimeter setting. Entering an altimeter setting will give a wrong answer at any airport above sea level.
Sources and basis (all opened 2026-10-08): US National Weather Service El Paso, Density Altitude Calculator (the page script is the source of the formulas above, and its text says to enter station pressure, not altimeter setting).
FAQ
What is density altitude?
The altitude in the standard atmosphere at which the air density equals the density in your actual conditions. Hot, humid, high-elevation air has a higher density altitude.
What is the density altitude at 35 degrees C, 15 degrees C dew point and 24.90 inHg?
About 8,583 feet (2,616 metres), by the National Weather Service formula.
Should I enter the altimeter setting or station pressure?
Station pressure, the actual pressure at your location. The National Weather Service calculator this tool follows says not to use the altimeter setting.
Does humidity matter?
Yes, slightly. Water vapour makes air less dense, so a higher dew point raises the density altitude. This tool includes it through the virtual temperature.
Can I use this for flight planning?
No. Use the aircraft flight manual, official weather data and your own judgement. This is a general-interest calculation.
Not for flight planning
This reproduces a published weather-service calculation for general information. Do not use it for aircraft performance, take-off or flight-safety decisions. Use the aircraft flight manual and official aviation weather sources.