Pressure Altitude Calculator

How it works

Pressure altitude = field elevation + (29.92 − altimeter setting) × 1,000.

Each 0.01 inHg is worth about 10 ft, and each hectopascal about 27 ft. When the pressure is lower than standard, pressure altitude is higher than your true elevation — which is the direction that hurts performance.

Why performance charts want it

An aircraft does not care about height above the sea. It cares about the density of the air going through the propeller and over the wing, and pressure altitude is the first half of that story — temperature, via density altitude, is the second.

The other reason it matters

Flying from high pressure to low pressure without resetting the altimeter leaves you lower than indicated. "High to low, look out below" is the mnemonic, and it is worth keeping because the error is in the dangerous direction.