Psychrometric Graph Online

This is the temperature at which the air becomes saturated (100% RH) if cooled at constant pressure. To find it, move horizontally left from your point to the saturation curve.

These are straight horizontal lines measuring the actual mass of water vapor per mass of dry air (grains/lb or g/kg). This tells you how much moisture is in the air.

These are sweeping parabolic curves. Each curve represents a percentage of saturation (0% to 100%). The 100% RH line is the Saturation Line . Air cannot hold more moisture beyond this line; it will start to condense (dew, fog, rain). psychrometric graph

Once you learn to see the air through these lines, you will never look at a cloudy window or a sweat glass of iced tea the same way again. You are seeing psychrometrics in action. Standard psychrometric charts are published by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) and are available for various altitudes.

Air is invisible. Yet, for heating, ventilation, and air conditioning (HVAC) engineers, it is a complex mixture of gases, water vapor, and energy. To visualize this invisible world, engineers rely on one of the most elegant and powerful tools ever developed: The Psychrometric Chart . This is the temperature at which the air

These are slightly sloped diagonal lines indicating the volume occupied by a unit mass of dry air (cubic feet per pound). This is critical for sizing fans and ducts.

Often described as a "graph of the physics of air," the psychrometric chart might look like a chaotic spiderweb of lines at first glance. However, once you learn its language, it becomes an indispensable map for controlling comfort, preserving food, drying paint, or even keeping a data center cool. Psychrometry is the study of the thermodynamic properties of gas-vapor mixtures—specifically, air and water vapor. The chart doesn't just plot temperature; it plots the relationship between heat, moisture, and energy. This tells you how much moisture is in the air

These are diagonal lines sloping downwards to the right. The wet bulb temperature is measured by a thermometer with a wet wick. It represents the cooling effect of evaporation. Along the saturation line, WBT = DBT.