What Is QNH in Aviation?
Quick answer: QNH is a pressure setting that makes an aircraft's altimeter indicate altitude above mean sea level. QFE uses a local aerodrome or runway reference, while the standard pressure setting (1013.25 hPa) is used for pressure altitude and flight levels.
QNH, QFE and QNE: What's the difference?
Term | Simple meaning | What the altimeter shows |
QNH | Local pressure setting for altitude referenced to sea level | Approximately the aerodrome's elevation when on the ground at its reference point |
QFE | Pressure at a specified aerodrome or runway reference point | Approximately zero at that reference point |
Standard pressure (often called QNE) | Fixed setting of 1013.25 hPa / 29.92 inHg | Pressure altitude, used for flight levels |
An easy example
Imagine an airport at 1,500 feet above sea level. When your aircraft is on the ground at the airport's reference elevation:
- Set the correct QNH: the altimeter reads about 1,500 feet.
- Set the corresponding QFE: it reads about zero.
- Set standard pressure: it shows pressure altitude, which depends on the actual weather pressure.
The aircraft hasn't moved. Only the pressure reference has changed.
Why does this matter?
Pilots use the appropriate altimeter setting to understand their vertical position and follow air traffic procedures. QNH does not tell you your height above the terrain directly below you. Flight levels use standard pressure, and the point where settings change depends on local procedures.
Quick questions
Is QNH always 1013 hPa? No. Local QNH changes with the weather. 1013.25 hPa is the standard setting.
Does QFE always show zero at an airport? Only at the specific reference point for that QFE, when the altimeter and setting are correct.
Is QNE exactly the same as standard pressure? Terminology varies. The FAA uses QNE for the standard altimeter setting, while the UK Met Office defines QNE differently. For flying, follow the terminology and procedures specified by your aviation authority.
Official references
1. FAA Pilot/Controller Glossary: QNH, QF[1] [2] E and QNE
2. UK Met Office: Aviation abbreviations
3. FAA Aeronautical Information Manual: Altimeter setting procedures
For education only. Have an aviation instructor verify this article before publication; always follow current local regulations, aircraft procedures and ATC instructions.