# Altitude to PSI question

1. May 2, 2016

### SanSan

• Thread moved from the technical forums, so no HH Template is shown.
I have an altitude to psi problem that I can't quite figure out. I know I have to use conversions, but I'm not sure how to set them up.

At an altitude of 35,000 ft, atmospheric pressure is less than 0.500 atm. Convert this pressure to pounds per square inch (psi).

2. May 2, 2016

### Nidum

Atmosphere pressure is approximately 14.7 psi at sea level .

So if you know that atmospheric pressure at a specified altitude is 0.5 sea level value then pressure in psi = 14.7 * 0.5 .

nb: The 14.7 psi pressure at sea level is commonly referred to as ' one atmosphere ' .
So two atmospheres = 29.4 psi . Three atmospheres = 44.1 psi etc .

3. May 2, 2016

### SanSan

Thank you for your help. I misinterpreted the question.

4. May 2, 2016

### Staff: Mentor

Actually it would be better to look for the definitions of atm and psi and see how to convert between them using conversion factors. While there is nothing with the approach suggested by Nidum, using conversion factors is much more universal and allows conversion between any compatible units.

https://en.wikibooks.org/wiki/FHSST_Physics/Units/How_to_Change