Pressure altitude from the altimeter setting

Pressure altitude for any altimeter setting other than 29.92" (TC AIM AIR 1.5.3-1.5.4):

PA = indicated + (29.92 − setting) × 1000

• PA: pressure altitude
• indicated: indicated altitude
• setting: altimeter setting, inHg

Setting below 29.92" (TC AIM AIR 1.5.3):

• Standard datum below you
• PA reads higher than indicated
• Example: 29.42" pushes PA above indicated, not below

Unit trap: if setting in hPa, convert first: 29.92" = ~1013 hPa, 1 inHg = 33.86 hPa, so ~29.5 ft per hPa (do not reuse 33.86 as the feet-per-hPa factor).

Practice