Pressure Altitude Calculator
Enter your airport field elevation and current altimeter setting to calculate pressure altitude for preflight planning and performance checks.
What Is Pressure Altitude?
Pressure altitude is the altitude indicated when the altimeter is set to the standard pressure of 29.92 inHg (1013.25 hPa). In practical terms, it is your height above the standard datum plane, not necessarily your exact height above sea level under current weather conditions.
Pilots use pressure altitude as a foundational input for aircraft performance charts, especially when calculating takeoff distance, climb performance, and engine output. It is one of the first numbers you should verify during preflight performance planning.
Why This Number Matters in Flight Planning
Even if you fly from the same airport every day, changing atmospheric pressure can significantly impact aircraft performance. A lower pressure day generally means higher pressure altitude, and that can reduce performance.
- Longer takeoff roll
- Reduced climb rate
- Potentially lower engine and propeller efficiency
- More conservative loading and runway decisions
Pressure altitude is also used to derive density altitude, which factors in temperature and provides an even clearer picture of how the airplane will perform.
How to Use the Pressure Altitude Calculator
Step 1: Enter Field Elevation
Use the airport elevation from your chart supplement, airport diagram, or trusted flight planning source. Select feet or meters to match your value.
Step 2: Enter Local Altimeter Setting
Use the latest altimeter setting from ATIS, AWOS/ASOS, METAR, or your local weather source. Choose inHg or hPa depending on your region and data source.
Step 3: Review the Output
The calculator returns pressure altitude in both feet and meters, along with the inHg conversion used in the formula so you can quickly verify the math.
Quick Worked Example
Suppose your field elevation is 5,000 ft and your altimeter setting is 29.42 inHg.
Pressure Altitude = 5,000 + (29.92 - 29.42) × 1000
Pressure Altitude = 5,000 + 0.50 × 1000 = 5,500 ft
That means your aircraft will perform as if it were operating from 5,500 feet under standard pressure assumptions.
Pressure Altitude vs Density Altitude
Pressure Altitude
Depends on elevation and barometric pressure only.
Density Altitude
Builds on pressure altitude and adds temperature effects. On hot days, density altitude can be dramatically higher than pressure altitude, often creating the highest performance risk for light aircraft operations.
Common Mistakes to Avoid
- Using stale altimeter settings from old weather reports
- Mixing hPa and inHg without converting units
- Skipping performance calculations for short familiar flights
- Assuming sea-level performance at high-elevation fields
Safety Reminder
This tool is for planning support and educational use. Always cross-check calculations with your POH/AFM performance charts, current weather, runway condition, aircraft weight and balance, and operational regulations before flight.
Frequently Asked Questions
Can pressure altitude be below field elevation?
Yes. If the altimeter setting is higher than 29.92 inHg, pressure altitude will be lower than the field elevation.
Do I need pressure altitude if I already have GPS altitude?
Yes. GPS altitude is not a replacement for performance planning altitude. Aircraft performance charts rely on pressure altitude and temperature-based density altitude.
Is this calculator useful for helicopter operations too?
Absolutely. Helicopter performance planning also relies on pressure altitude and density altitude, especially in high/hot conditions.