Pressure Altitude Calculator
Pressure altitude = field elevation + (29.92 − altimeter setting in inHg) × 1,000 ft, so a 2,000 ft airfield with an altimeter of 29.42 inHg has a pressure altitude of 2,500 ft.
For general informational use. Verify critical aviation calculations and weather with an authoritative source.
Pressure altitude corrections at a glance
Pressure altitude is field elevation corrected for the day’s pressure: about 1,000 ft per inch of mercury, or about 27–30 ft per hPa near sea level. Low pressure means a higher pressure altitude.
| Altimeter (inHg) | Same in hPa | Correction to add to elevation |
|---|---|---|
| 29.42 | 996.3 | +500 ft |
| 29.62 | 1003.0 | +300 ft |
| 29.82 | 1009.8 | +100 ft |
| 29.92 | 1013.2 | 0 ft |
| 30.02 | 1016.6 | −100 ft |
| 30.22 | 1023.4 | −300 ft |
| 30.42 | 1030.1 | −500 ft |
Where pressure altitude is used
- Performance charts: take-off, climb and landing charts in most flight manuals are entered with pressure altitude and temperature.
- Flight levels: above the transition altitude everyone sets 29.92 inHg or 1013 hPa, so the altimeter shows pressure altitude and aircraft are separated on a common reference. See Flight Levels Explained.
- True airspeed and density altitude: both start from pressure altitude.
- Transponder altitude reporting: Mode C and Mode S report pressure altitude; ATC’s system corrects it for the local setting.
Quick check in the cockpit
On the ground, set 29.92 (or 1013) in the altimeter window and read the altimeter: that is the field’s pressure altitude right now. Remember to reset the local setting before departure.
Common mistakes
- Applying the correction with the wrong sign. If the setting is below standard, pressure altitude is above field elevation.
- Mixing units: 1 inHg is 33.86 hPa, so a 10 hPa difference is about 0.30 inHg, or roughly 300 ft.
- Using the “1,000 ft per inch” rule high up. It is a sea-level approximation; the tool’s result is accurate for normal airfield elevations.
Pressure altitude in plain terms
Pressure altitude is the height shown on an altimeter set to standard pressure: 29.92 inHg or 1013.25 hPa. It is the starting point for aircraft performance charts, density altitude and true airspeed, and it is what flight levels are based on above the transition altitude.
How to use it
- Enter the field elevation in feet.
- Enter the altimeter setting from the METAR, ATIS or tower.
- Choose inHg or hPa.
- Read the pressure altitude and the correction applied.
Method and calculation
Pressure altitude = elevation + (29.92 − altimeter setting in inHg) × 1,000 ft. When the setting is in hPa it is converted to inHg first (divide by 33.8639). The 1,000 ft per inHg factor is the standard FAA rule of thumb and is accurate enough for performance planning near the surface.
Worked example and practical notes
Field elevation 1,000 ft with an altimeter setting of 30.12 inHg: 29.92 − 30.12 = −0.20, so the correction is −200 ft and pressure altitude is 800 ft. With QNH 1020 hPa (30.12 inHg) the result is the same.
Accuracy and practical tips
High pressure gives a pressure altitude below field elevation; low pressure gives one above it. For the full picture on a warm day, continue to the Density Altitude Calculator.
Method based on the standard atmosphere and FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25) rules of thumb. Use your aircraft flight manual (AFM/POH) and approved flight-planning tools for real operations.
Last reviewed: October 2026
Read the guide: Density Altitude Explained: Hot and High Days
Frequently asked questions
When is pressure altitude equal to field elevation?
When the altimeter setting is exactly 29.92 inHg or 1013.25 hPa.
Why do performance charts use pressure altitude?
Because aircraft and engine performance depend on air pressure and temperature, not on height above sea level.
What is the hPa version of the rule?
About 27–30 ft per hPa near sea level. The calculator converts to inHg and applies 1,000 ft per inHg.
Is pressure altitude the same as a flight level?
A flight level is pressure altitude in hundreds of feet, so FL080 is a pressure altitude of 8,000 ft.