How do you convert altimeter setting 30.12 pressure?

Answer 1

First, determine the difference from standard pressure 29.92.

30.12

-29.92

---------

.20

If you drop the decimal point and add a zero you get the number of feet of difference, so .20 = 200 feet. Since 30.12 is a higher number than 29.92, you subtract it from the actual altitude. If the indicated altitude is 10000 feet, your pressure altitude is 9800 feet. If your altimeter setting is lower than 29.92 you add the difference.

It can also be expressed as PA = IA + ((29.92 - AS) * 1000) where IA is indicated altitude and AS = altimeter setting.