How to use this calculator
- Enter field elevation. Use the airport or runway elevation.
- Enter altimeter setting. Use the current pressure setting in inches of mercury.
- Enter OAT. Use outside air temperature in degrees C.
- Read density altitude. Use the result as a quick performance context only.
How it works
Pressure altitude is estimated as field elevation + (29.92 - altimeter) x 1000 ft. ISA temperature is 15 - 1.98 x altitude_thousands, then density altitude is approximated from the ISA deviation.
Use it with climb gradient, stall speed and weight and balance.
Worked example
Verified against the live calculator
At a 5,000 ft field, 29.92 inHg altimeter and 30 C OAT, ISA temperature is about 5 C and density altitude is roughly 8,000 ft.
Frequently asked questions
How is density altitude estimated here?
It estimates pressure altitude from elevation and altimeter setting, then adds 120 ft per deg C of ISA temperature deviation.
What is pressure altitude?
Pressure altitude is field elevation corrected to a standard 29.92 inHg pressure setting.
Does humidity matter?
Humidity can affect performance, but this quick estimator does not model it.
Can this replace takeoff performance charts?
No. Use approved performance charts, current weather and runway data for operational planning.
Method & assumptions
- Uses a common dry-air quick estimate, not a full atmospheric model.
- Does not replace aircraft performance charts, runway analysis, NOTAMs, weather observations or flight manual limitations.