Psychrometric Chart Calculator

Input Parameters

Unit System:

SI IP

Dry Bulb Temperature: °C

Select Second Parameter:

Wet Bulb Temperature: °C

Relative Humidity: %

Dew Point Temperature: °C

Altitude: m

Results

Atmospheric Pressure: – kPa

Saturated Vapor Pressure: – kPa

Partial Vapor Pressure: – kPa

Water Vapor Content: – kg/kg dry air

Relative Humidity: – %

Dew Point Temperature: – °C

Wet Bulb Temperature: – °C

Enthalpy: – kJ/kg

Specific Volume: – m³/kg

Calculation Explanation

Enter values to see calculation explanation.

What is a Psychrometric Chart?

A psychrometric chart is a graphical representation of the physical and thermodynamic properties of moist air. It serves as a fundamental tool for HVAC engineers, meteorologists, and building science professionals to analyze and visualize the relationship between various air properties such as temperature, humidity, enthalpy, and density.

The chart displays multiple parameters simultaneously, including:

Dry bulb temperature (the temperature measured by a standard thermometer)
Wet bulb temperature (the temperature measured by a thermometer covered with a wet cloth)
Relative humidity (the ratio of actual water vapor pressure to the saturation vapor pressure)
Humidity ratio or absolute humidity (the mass of water vapor per unit mass of dry air)
Enthalpy (the total heat content of the air)
Specific volume (volume per unit mass of dry air)
Dew point temperature (the temperature at which condensation begins)

Understanding these relationships is crucial for designing efficient HVAC systems, analyzing building comfort conditions, and solving various engineering problems related to air conditioning, dehumidification, and ventilation.

How to Use the Psychrometric Chart Calculator

Step 1: Select your preferred unit system from the options at the top of the calculator. Choose “SI” for metric units (°C, kPa, kg/kg) or “IP” for imperial units (°F, psia, gr/lb).

Step 2: Enter the dry bulb temperature value in the first input field. This is the standard air temperature measured with a regular thermometer and serves as the primary input for all psychrometric calculations.

Step 3: Select the second parameter you want to use from the dropdown menu. You have three options:

Wet Bulb Temperature: The temperature measured by a thermometer wrapped in a wet cloth
Relative Humidity: The percentage of moisture in the air relative to what it could hold at that temperature
Dew Point Temperature: The temperature at which condensation begins to form

Step 4: Enter the value for your selected second parameter in the corresponding field. Also, input the altitude if your location is significantly above sea level, as atmospheric pressure affects psychrometric calculations.

Step 5: Click the “Calculate” button to generate comprehensive results. The calculator will display all psychrometric properties including atmospheric pressure, vapor pressure, humidity ratio, enthalpy, and specific volume. Review the detailed explanation provided below the results to understand how these values were derived and their significance in air analysis.