The Interactive Psychrometric Chart
for HVAC Engineers

Yes — basic access to the psychrometric chart is free and requires no registration. More features available with complete registration.

Calculations follow ASHRAE Fundamentals 2021, Chapter 1 (SI), using the Hyland-Wexler equations. The maximum deviation of saturation pressure against the ASHRAE reference tables is 0.041 %.

Yes. PsychroView exports the chart as DXF for AutoCAD, as well as vector PDF and PNG at any resolution. Results tables can also be exported to Excel, Word and HTML.

You can start calculating without an account. A free account saves your projects and raises the limits of anonymous mode, so it is the practical way to chain processes and model a whole air circuit in a single project.

A psychrometric chart (sometimes called a humidity chart, and often misspelled “psychometric chart”) is a graphical representation of the properties of moist air — dry-bulb temperature, humidity ratio, enthalpy and relative humidity. HVAC engineers use it to plot and size air-handling processes such as heating, cooling, humidification and dehumidification.

Both show the same thermodynamic data for moist air; they differ in axis convention. The Mollier h-x diagram, common in Europe, is effectively a rotated version of the ASHRAE-style psychrometric chart used in North America. PsychroView lets you work in either view.

Find the dry-bulb temperature on the horizontal axis and go straight up to the relative humidity curve — that point is the air state. Read the humidity ratio on the right-hand axis. Moving horizontally to the left until you reach the saturation curve gives the dew point; following the sloping wet-bulb line up and to the left to the saturation curve gives the wet-bulb temperature, and a line parallel to it leads to the enthalpy scale. PsychroView reads out all of these values for every point you plot.

Yes. For every state point PsychroView calculates the dew point, wet-bulb temperature, enthalpy, humidity ratio, relative humidity, specific volume and density per ASHRAE Fundamentals 2021. For a quick single answer, the articles also include dew point, wet-bulb, enthalpy and humidity ratio calculators.

On the Downloads page: blank Mollier h-x and Carrier psychrometric charts as vector PDF (A4 and A3), SVG or DXF, in SI and I-P units. They are free and need no sign-up.