Psychrometrics provides you with psychrometric air properties given two properties as input values at a known altitude or atmospheric pressure. The properties are determined using the ideal gas law for the behavior of air. Once the properties are determined, the point is indicated on the psychrometric chart. Process lines can be connected between any two known points, which can provide you with the differences involved in moving from one point to the next. In addition, the program allows you to perform some basic HVAC calculations that depend on psychrometrics. Please note that you can use both US and Metric units.