Gas compressibility factor

Brief

gas compressibility factor is the ratio of the Real Gas volume to the Ideal Gas volume, which is a measure of the amount that the gas deviates from the perfect behavior.

$z = \frac{Actual\ volume\ of\ gas\ at\ specified\ T\ and\ P}{Ideal\ volume\ of\ gas\ at\ same\ T\ and\ P}$

Nomenclature

$P$ = Pressure, psia

$T$ = temperature, °R

$z$ = gas compressibility factor, dimensionless