Altimetry
Pressure altitude, the standard temperature for it, density altitude, and cold-day corrections.
Pressure altitude, the standard temperature for it, density altitude, flight levels, the QNH, QFE, and QNE settings, and cold-temperature corrections. Pilots use these tools before a hot or high departure, when planning a flight level, and when flying approaches on a cold day. Start with pressure altitude, then carry it into density altitude. Remember that the altimeter reads correctly only in standard temperatures: in cold air you are lower than it shows, which the cold temperature tool corrects for.
Planning and education aid. Not for primary navigation. Full disclaimer
I want to convert between QNH and QFE, or work out the altimeter setting
- QNH, QFE, and QNE
Converts between the altimeter setting (QNH) and station pressure (QFE) at an airport, gives the field's pressure altitude (QNE), and works out the altimeter setting from a barometer reading.
I want to find the lowest usable flight level or a flight level's altitude
- Flight level and altitude
The altitude on the local altimeter setting that a flight level puts you at, or the other way round, with the US lowest usable flight level and transition altitude.
I want to correct approach altitudes for a cold day
- Cold temperature altitude correction
How much to add to each procedure altitude when the airport is colder than standard, by the ICAO equation, with the 4% rule and the ICAO table beside it.
I want to find my true altitude in cold or warm air
- True altitude
Your true height above sea level from the altimeter reading when the air is colder or warmer than standard: high to low, look out below.
I want to find pressure altitude from field elevation and the altimeter setting
- Pressure altitude
Pressure altitude from field elevation and the altimeter setting, exact from the standard atmosphere, with the 1,000 ft per inch rule of thumb beside it.
I want to know how far today's temperature is from standard
- ISA temperature and deviation
The standard temperature at a pressure altitude (15 °C falling 1.98 °C per 1,000 ft to -56.5 °C), and the ISA deviation of an outside air temperature.
I want to find density altitude for takeoff and climb performance
- Density altitude
How high the airplane feels: density altitude from field elevation, altimeter setting, and temperature, with optional dew point, and the rules of thumb beside it.
Field elevation to density altitude
- Start from field elevation and the altimeter setting: the difference from 29.92 inHg (1013.25 hPa) gives pressure altitude. Pressure altitude
- The standard atmosphere gives the temperature expected at that pressure altitude; the deviation says how much warmer or colder today is. ISA temperature and deviation
- Pressure altitude and outside air temperature give density altitude, the altitude the airplane performs as if it were at. Density altitude
Guides that use these tools
- VFR preflight: From the latest METAR to pressure altitude, density altitude, and the crosswind on your runway.