QFE is a Q code used by pilots and air traffic control to refer to the current air pressure which will calibrate the pilot's altimeter to give actual height above the ground at a particular airfield. This setting is used during take off and landing and when flying in the circuit. A mnemonic for the code is "Q Field Elevation".

ATC will update pilots with the QFE when necessary. A typical radio conversation might go:

  • Pilot: Golf Whiskey Alpha Charlie Foxtrot, requesting taxi clearance for local VFR
  • ATC: Golf Charlie Fox, taxi to Alpha for 25 right hand, QFE niner-niner-eight millibars
  • Pilot: To alpha, 25 right, QFE niner-niner-eight, Golf Charlie Fox

Here, the pilot of G-WACF requests a taxi clearance (he's on the ground), and he's told to taxi to (holding point) A for runway 25, right hand circuits, and the QFE is 998 millibars. The pilot acknowledges the information he's given, as required.

In most parts of the world, QFE is given in millibars (or hectopascals, which is the SI unit). In the USA, QFE is given in inches of mercury.