Calculated Point Values

Calculated Process Changes

All processes are calculated with actual densities.

= Dry Bulb Temperature
= Wet Bulb Temperature
= Dew Point Temperature
= Absolute Humidity
= Enthalpy
= Relative Humidity
= Air Density
= Vapor Pressure

Input section
Air start conditions
Air flow


Sensible Heat Factor

Process 0 1


Process 1 2


Process 2 3


Process 3 4


Process 4 5





Online Interactive Psychrometric Chart

With a Psychrometric Chart (also know as Mollier Diagram) you can draw processes of humid (moist) air and calculate air conditions. This diagram is widely used in mechanical engineering and HVAC technology and plots the Temperature versus the Absolute Humidity. The chart is is combined with the Relative Humidity lines and the Enthalpy to calculate the change in total internal energy.
The Psychrometric Chart is also known as the "Mollier-Diagram". At the Thermodynamics Conference in Los Angeles (1923), it was decided to name the diagram after Richard Mollier in his honor.

Psychrometric Chart calculator and Sketcher

With this online tool you can simulate and visualize thermodynamic processes that affect moist air.
After entering the Air start conditions, you can enter various actions, like "Mix", "Heat", "Cool", "Heat Recovery" and "Humidify".
The new condition of the air is calculated and this new point and the process will be automatically drawn in the diagram.


Set the chart according to your needs:
  • Chart Style: Mollier/ Psychrometric-Chart. The x/y-axes will be flipped
  • Units-system can be set to Metric(SI) or Imperial(I-P). This affects the chart, input values and calculated values.
  • Altitude: Standard the altitude is set to sea level. Because the formulas and the graph depend on the height above sea level (air pressure changes), it is important set the correct altitude.
  • Axes: Do you want to focus on just a part of the diagram?
  • Comfort area: This is the range of the desired Temperature and Humidity. On/Off or customizable.

PDF report

If you want to save your Diagram and Values/ processes in a PDF-report, please push the button "Save PDF", and it starts downloading automatically.

Dry Bulb Temperature - Tdb
The temperature axis in the diagram is also know as the dry bulb temperature (Tdb). This parameter is popularly known as temperature when people read the thermometer.
The dry bulb temperature is called "dry bulb" because the measured temperature is not affected by any moisture in the air.

  • Degrees Celsius(°C). Zero Kelvin equals to -273°C.
  • Degrees Fahrenheit(°F) - Imperial units

Wet Bulb Temperature
The Wet Bulb Temperature (Twb) represents the air temperature when fully adiabatic saturated (100% Relative Humidity). To make it more understandable: it is the temperature of a wet object in an air flow.
When the air flow is not saturated, moisture of the wet object will evaporate (adiabatic process) in the air which results in a lower temperature of that object; the wet bulb temperature of the air.
When the air flow is saturated (100% RH), the temperature of the air flow is equal to the wet bulb temperature of the air.
Adiabatic humidification follows the wet-bulb tempeprature lines and is slightly different from following the enthalpy-lines.

  • Degrees Celsius(°C) at 100% Relative Humidity
  • Degrees Fahrenheit(°F) at 100% Relative Humidity - Imperial units

Dew Point Temperature
The Dew Point Temperature (Tdew) is the temperature where water vapor starts to condensate from the air. At lower temperatures the air can not hold the amount of water.
Like the Wet Bulb Temperature the Dew point Temperature is also fully saturated (100% Relative Humidity).
The absolute humidity of a random given air condition is the same as its Dew Point Temperature.

  • Degrees Celsius(°C) at 100% Relative Humidity
  • Degrees Fahrenheit(°F) at 100% Relative Humidity - Imperial units

Absolute Humidity
Absolute Humidity (X) is the actual amount of water vapour that is absorbed by the air, regardless of the temperature of the air. Because it is not affected by the temperature, the volume of the air is also inrelevant. Therefore this parameter is given as a weight ratio:
  • grams per kilogram (g/kg)
  • millipounds per pound (mlb/lb) - Imperial units

Relative Humidity
The Relative Humidity (RH) is the the ratio in a percentage (%) of the amount of Absolute Humidity compared to the amount of moisture that would be present if the air were saturated at the smae temperature.
Relative Humidity is often abbreviated to "RH".
  • 100% RH means that the air is saturated.
  • 0% RH means that no moisture is present in the air.
  • 30% RH means that 30% of the possible moisture weight is absorbed.

Enthalpy (H) is know as the total amount of energy the air mixture. This energy can be expressed in sensible energy (absorbed temperature) and latent energy (absorbed moisture).
This means that an air mixture with a lot of moisture can have the same Enthalpy as air with less moisture absorbed but with an higher temperature.
  • kiloJoules per kilogram (kJ/kg)
  • British thermal unit per pound (BTU/lb) - Imperial units

Important to know when converting Enthalpy from metric to imperial units is that 0 kJ/kg is related to 0°C and 0 BTU/lb is related to 0°F (other zero point)