Welcome Guest. Sign in or Signup

7 Answers

Pressure Altitude Without an Altimeter Setting

Asked by: 4529 views Student Pilot, Weather

Is there a way to calculate pressure altitude at home before a flight if my airport doesn't report an altimeter setting?

Ace Any FAA Written Test!
Actual FAA Questions / Free Lifetime Updates
The best explanations in the business
Fast, efficient study.
Pass Your Checkride With Confidence!
FAA Practical Test prep that reflects actual checkrides.
Any checkride: Airplane, Helicopter, Glider, etc.
Written and maintained by actual pilot examiners and master CFIs.
The World's Most Trusted eLogbook
Be Organized, Current, Professional, and Safe.
Highly customizable - for student pilots through pros.
Free Transition Service for users of other eLogs.
Our sincere thanks to pilots such as yourself who support AskACFI while helping themselves by using the awesome PC, Mac, iPhone/iPad, and Android aviation apps of our sponsors.

7 Answers

  1. Best Answer


    ayavner on Jan 24, 2019

    Not really – you need that number to compare to standard (29.92″) so that you know how much to adjust up and down. You could probably get close if there is a forecast for that area that will provide that, but it may not be accurate at the time of the flight.

    As far as how to calculate it, it is about 1000′ per inch. So as an example if it is supposed to be 30.02″ tomorrow – then just take (29.92 – 30.02) * 1000 then add or subtract the result to the elevation. Higher pressure than standard means the PA will be lower than elevation, lower pressure means the PA will be higher. In this example,

    (29.92 – 30.02) = -.1

    -.1 * 1000 = -100′

    Elevation – 100′ = PA.

    Main thing to remember is the higher/lower relationship so you know what to expect and if your answer makes sense.

    Hope that helps?

    +2 Votes Thumb up 2 Votes Thumb down 0 Votes



  2. KDS on Jan 24, 2019

    You can make a good guess of it if there are nearby airports.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  3. Ticen on Jan 24, 2019

    Or to make it even simpler: every 100′ = .10 adjustment on Kollsman window (where you adjust altimeter setting). Increase .10, altimeter adjusts + 100, decrease .10, adjusts – 100′

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  4. John D Collins on Jan 24, 2019

    What are you using pressure altitude for? If all you are doing is determining the altimeter setting, when you get to the airport, set the altimeter to field elevation by adjusting the kollsman setting. If you have other needs for pressure altitude, set the altimeter setting to 29.92 and read the altitude to get the local pressure altitude.

    +2 Votes Thumb up 2 Votes Thumb down 0 Votes



  5. ayavner on Jan 24, 2019

    He may need it as a starting point for the chase charts for takeoff/landing performance?

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  6. DarthDecker on Jan 24, 2019

    Yeah I was just trying to get it for my performance charts and all that stuff from home.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  7. Kris Kortokrax on Jan 25, 2019

    I just looked at info for my home on the Weather Channel. It lists the barometric pressure and the temperature (all you need to calculate pressure or density altitude).

    You should be able to find the same info for your airport. If it is off by a tenth, that is a 100′ difference which will make no significant difference in the performance of your aircraft.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes


The following terms have been auto-detected the question above and any answers or discussion provided. Click on a term to see its definition from the Dauntless Aviation JargonBuster Glossary.

Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.