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An aircraft altimeter is a barometer. It measures air pressure and shows it as height. Because air pressure changes with the weather, the pilot has to tell the altimeter what pressure to use as its reference. That reference is the altimeter setting, and there are three common ones: QNH, QFE and QNE.
QNH: altitude above mean sea level
With QNH set, the altimeter reads altitude above mean sea level. On the runway it shows the airport elevation (approximately). QNH is the standard setting for take-off, landing and flight below the transition altitude in most of the world, because charts, obstacles and terrain are published as heights above sea level.
QNH appears in every METAR. In Q1009, QNH is 1009 hPa. In US reports, A2992 means 29.92 inches of mercury.
QFE: height above the airfield
With QFE set, the altimeter reads zero on the runway and shows height above the airfield. Some military operators and gliding clubs use it, and it was once common in parts of Europe and Russia. It is rarely used for commercial flights today.
QNE: standard pressure
QNE means setting the standard pressure of 1013.25 hPa (29.92 inHg). The altimeter then shows pressure altitude. Above the transition altitude, all aircraft use this setting and fly flight levels: FL350 means 35,000 ft on the standard setting. Because everyone uses the same reference, vertical separation works even as the local weather changes.
Transition altitude and transition level
- Climbing through the transition altitude, pilots change from QNH to standard (1013).
- Descending through the transition level, pilots change from standard back to QNH.
Transition altitudes are set by each country and sometimes by each airport. The United States uses 18,000 ft nationwide, while many other countries use much lower values. Always check the AIP or chart for the airport you are using.
Why the setting matters: a quick example
A rough rule is that 1 hPa equals about 27–30 ft near sea level. If the actual QNH is 993 hPa and the altimeter is still on 1013, the altimeter reads about 20 × 27 ≈ 540 ft higher than the aircraft really is. This is the origin of the saying “from high to low, look out below”: flying from high pressure into low pressure without resetting makes you lower than you think.
Converting hPa and inHg
- 1 inHg = 33.8639 hPa
- 1 hPa = 0.02953 inHg
- 1013.25 hPa = 29.92 inHg
For example, 1009 hPa × 0.02953 = 29.80 inHg. Use our QNH hPa / inHg Converter for exact values.
Summary
| Setting | Altimeter shows | Typical use |
|---|---|---|
| QNH | Altitude above mean sea level | Departure, arrival, below transition altitude |
| QFE | Height above the airfield | Some military, gliding and circuit training |
| QNE / 1013 | Pressure altitude (flight levels) | Above the transition altitude |
Related: How to read a METAR to find the current QNH, and the Feet / Metres converter for countries that assign altitudes in metres.
Educational content only. Follow your local AIP and operator procedures.
Worked example: from QNH to QFE and pressure altitude
An airfield is 450 ft above mean sea level and the QNH is 1008 hPa.
- QNH 1008 hPa: on the ground the altimeter reads about 450 ft, the airfield elevation.
- QFE: near sea level, pressure falls by about 1 hPa for every 27–30 ft of height. 450 ft ÷ about 27 ft per hPa ≈ 17 hPa, so QFE ≈ 1008 − 17 = 991 hPa. With QFE set, the altimeter reads about zero on the runway.
- Standard setting 1013 hPa: QNH is 5 hPa below standard, and 5 hPa × about 27–30 ft ≈ 140–150 ft, so the pressure altitude on the ground is about 590–600 ft.
These are rules of thumb for training. Air traffic services give QFE directly where it is used, and pressure altitude comes from setting 1013.25 hPa (29.92 inHg) on the altimeter.
Common mistakes
- Not resetting at the transition altitude or transition level. Climbing through the transition altitude, set standard pressure. Descending through the transition level, set QNH. Forgetting either produces a level error.
- Mixing up hPa and inHg. 1013 hPa and 29.92 inHg are both standard pressure, but entering “1013” as 30.13 inHg or “2992” as hPa is a classic error. Read back the units with the value.
- Using an old QNH on a long flight. Pressure changes along the route. “From high to low, look out below”: flying towards lower pressure without resetting leaves the aircraft lower than the altimeter shows.
- Assuming the transition altitude is the same everywhere. It is 18,000 ft in the United States and Canada, but varies by country and airport elsewhere. Check the chart or AIP for the airport you are using.
- Ignoring temperature. The altimeter is calibrated to ISA. In very cold air the aircraft is lower than indicated even with the correct QNH; see the cold temperature correction guide.
FAQ
Do pilots in the United States use QFE?
Generally no. US operations use the altimeter setting (QNH, given in inHg) below 18,000 ft and 29.92 inHg in Class A airspace. QFE is used by some operators and military units in other countries.
Is QNE a pressure setting?
Strictly, QNE is the altimeter reading on the runway with standard pressure set, which is the field’s pressure altitude. In everyday use pilots say “QNE” or “standard” to mean flying with 1013 hPa or 29.92 inHg set.
Sources and further reading
- AIM 7-2, Barometric Altimeter Errors and Setting Procedures
- 14 CFR 91.121, Altimeter settings
- FAA Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25) (flight instruments chapter)
- ICAO Doc 8168, PANS-OPS, Volume I (altimeter setting procedures)
Sources checked November 2026. Rules differ between countries and change over time: for real flights, use the current publications of the authority that applies to you, your aircraft flight manual and your operator’s procedures.